Cable budget in a rig

Yup

Cant really use simple rules of thumb. You need to think of cables as another component - one that completes the circuit with others gear.  So get / pay what you need to get the sound you want. Which is why working w/ a good dealer to home demo is so important.

As much as needed until you reach the point when you no longer hear any meaningful difference going higher.
And when you buy used you can sometimes get lucky and have $2.5k cables for $600.
It also depends on the complexity of your system. If you have one source component and integrated amp - that's one set-up, and if you have three source components, separate transport and dac, separate phono stage, preamp and power monoblocks - that's something different.
I could live with one of my $500 interconnects on $1200 phono stage but what do you know - I have $1500 cables on it and the $500 one is in the closet for rare cd player use, which is also in the closet. My speaker cables cost new as much as the speakers, and power cord for the integrated amp more than the amp. All bought used except two pairs of interconnects. Now all my active components sound as good as they can, I believe. Soon it will be time to build a completely new system.
However, if you want the simplest answer to your question, I would say 20% new, generally speaking. Tonearm cable is very important if you think about playing records or play them already.
Each cable is a component and all of them much more so.

Thanks guys, my system will be in the 100K price range for preamp, monoblocks, DAC and music server all separates.Therefore i should look at 10-15K for cables ?

This is one seriously expensive system. Cost will also depend on the length of cables and power cords, and also on your hearing. In my view, really good interconnects and power cords start at about $1500 and speaker cables at about $2000, digital cable I am not sure, probably $1000 or so. But you should listen if you can, there is no reason to pay more than needed. One brand approach is simpler but not always the best. Some say that if one runs balanced XLR interconnects, especially if the equipment is fully balanced, the cables can be of lesser quality and lower price. Can be in some cases but I don't take it as an axiom. Sometimes $500 cables are overpriced and $1500 are not, and sometimes both are about right, considering overall crazy prices of good stuff.

Yes this will be my end game system for the next 20+ years.

In one system I have, the cables are roughly 50% of the equipment cost to me, not counting any power conditioning.  This is a lower cost office system, and this is where I landed as providing the best overall sound for dollars invested.

In my main system at home, my investment in cabling is currently about 20%, but I would be willing to go up from there if it yielded significant results.

I would say for a system costing what you suggest, you could build a very reasonable cable solution for 15% of the system value, particularly if you are buying some pieces used.  Understand, with the resolution capable in a system at that price point, you may continue to realize significant added value from rather exotic (and expensive) cable designs, and find the comment that cables are just another critical component in your overall design hold particularly true.

Choosing the right cables can be both exhausting and rewarding.

For audiophiles who know exactly what they are dong, there is not a percentage. For folks who may be unsure.. Then the budget audiophile should start with a 10% for all cables. For the op here, with a $100,000 system The ten percent would be perhaps for interconnects, and another 5% for powercords. The op should also invest in power conditioning. AudioQuest Niagara 7000 would be my suggestion. And dedicated powerline(s) with some fancy AC duplex.With the budget the op has... I would suggest contacting "The Cable Company" to have some cable loans to try out.

 Good suggestion Elizabeth to try before you buy.

For audiophiles who know exactly what they are dong, there is not a percentage. For folks who may be unsure.. Then the budget audiophile should start with a 10% for all cables. For the op here, with a $100,000 system The ten percent would be perhaps for interconnects, and another 5% for powercords.

Hmmmm....I swear there’s a Freudian slip in there somewhere. 

knownothing
Good suggestion Elizabeth to try before you buy.

Good one, knownothing (gosh, I like saying that) but Lizzie is our poster child for not (rpt not) trying before you buy. She hasn’t left home in fifteen years as far as we know. 

Guys obviously i will have a dedicated room with room treatment and dedicated powerline for such an investment.

I use to actually have a job, Geoff. So make that only EIGHT YEARS, NINE MONTHS since I have not left home. Actually I do leave my apartment and wander the halls at night, Yodeling softly. Only yodeling really loud when I get close to the Manager’s apartment.
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It is true I just buy stuff like cables without trying it out. But then being ’my own guru’ I have to. If I depended on someone else for advice? What sort of guru would I be??? So I never take advice from anyone.(well not totally true. I did accept my Dealer’s advice to NOT buy a new amp to go with my new Magnepan 20.7s.) ((And I actually thought about Geoff’s advice to buy a Hurricane powercord for more than fifteen seconds.))  *************************************************************************
For the op.. One suggestion is to not spend a lot on the cables or power cords until you have listened to the system for a few months. Then you will KNOW it a lot better, and can THEN listen when adding wires and know what the wire is doing, vs no clear abiilty to know with everything new. (this is assuming you wish to fiddle with the system to some extent... rather than just buy once and forever let it stay the same.)

You didn't tell us anything about your coming equipment. What is it ?

For the digital front end i made up my mind for Totaldac d1-Twelve mk2 + d1-server.For the pre-power combo i yet have to choose between Ypsilon PST-100 mk2 preamp + Aelius ll monoblocks or Aries Cerat Impera ll Ref preamp + Concero 65 Ref monoblocks or CH Precision L1+X1+M1 stereo or Gryphon Pandora preamp + Antileon Evo stereo or Nagra Classic preamp + Nagra MPS + Luxman M-900U monoblocks.

Wow, you are thinking in the right direction. I would also add Studer deck and some turntable to it. Never mind.
And what are your speakers going to be ?

Don't know about the others, first cables to try with Gryphons are Gryphon cables, then maybe something else too. With Ypsilon - Stage III Concept cables.

The speakers are the ones i own Thiel CS 3.7s.I have already demoed the Ypsilon separates at home in 2017.I'm going to Switzerland oct 23 to demo the Aries Cerat pre-power on the 3.7s.Will also stop by Geneva to make a factory tour at Dartzeel and listen to the new separates.

Great plan. Speaking of transistor and hybrid electronics, at this level I too would consider Ypsilon, Gryphon and Swiss brands. I would add Lamm to this company, and I am sure there are others I am not aware of. I probably would not combine Nagra with Luxman but who knows ? How did Thiels sound with Ypsilon ?

Ypsilon sound phenomenal on the Thiels, ultra refined sound without any harshness, very emotional.I'm sure Aries Cerat monos will be at least at the same level if not better.Regarding Swiss brands CH Precision is the only one i'm considering, the smoothest and tubey of the Swiss SS brands.It's also the most expensive brand of them all therefore my dealer better give me a good discount if i go this route.

But you mentioned DarTzeel and Nagra, both Swiss. I have never heard of Aries.

Dartzeel NHB-108 model 2 will not be able to drive my speakers unfortunately.I will demo in Paris Luxman M900U paired with Nagra Classic preamp mid november.This combo is the last one on my shortlist.Aries Cerat is my favorite tube brand at any price.

I personally wouldn't buy anything before auditioning Ypsilon and Gryphon, but that's me. I also happen to like both designers, watched a number of videos on youtube. Read about them too. If a designer makes no impression on me - I don't even consider his equipment, especially at this level.

Less than 1%. I suggest that you buy cheap and get used to the system. Then upgrade if and only if someone can demonstrate a positive difference in your system, at your leisure.