cost of speakers in relation to the rest of the system

personally I never held with the 30%+ of your system in speakers and use speakers that are <<10% of my system cost. Matching the speakers to the room and the system to the speakers will likely pay back much more assuming you have a decent set of speakers to begin with. My bias is always to spend more on sources being of the garbage in garbage out school

+1 Almarg

If you want realistic sound levels then the speakers should be easily more than 50 - 80% of your investment.

Speakers are one of the few items where diminishing returns does NOT come into play until you hit astronomical prices...this is because realistic dynamics with low distortion at high SPL (needed for a true "you are there" experience) requires very large heavy cabinets with large woofers and very high quality transducers...all this is extremely expensive and there is absolutely no way around this except maybe a pair of good headphones....

Diminishing returns for speakers probably starts around $50,000 whereas for other components it can be between $2000 to $5000

Of course if realistic SPL reproduction  (loud & true full range) is not required then YMMV as modest speakers with small 8 or 6 inch woofers can often do quite well at low SPL 

My amp, preamp, CD player, analog set up, all have a fairly close MSRP. Speakers msrp somewhat more than double of each. But for my Salk Songtowers in bedroom, other items list for quite more. Though Salk is sold direct. And like Al mentioned I do not need deep bass or loud volume in that system.

I'm a real value oriented kind of guy with my Focals and Pass amp. 
Focal 936's and Pass F5 clone, that is. 
I bought the speakers new and I love them. I built the amp. I built the speaker cables. And I restored the old Marantz feeding the Pass. It's an ongoing project. I don't have the money to blow on silliness just to see how it sounds. I have to evaluate what I've got, figure out what's going to improve it, and figure out how to make it or get it at a reasonable price. 
The amp cost just under $1000 to build and I built it like a beast. It's definitely worth of the speakers. The cables we're under $75. I need to figure out what to do with the Marantz now. Listening this well could cost a lot more money than I've spent. 

Maggies are known for their price/performance so that will affect the ratio...

I only paid $4,000 for my 3.7i's (retail is $6,400) and am pretty happy with them.   My ARC pre-amp was used, and so was my DAC.  CD Player was new; can't recall if the Sunfire amp was new or used...

but yes, it's like buying wine - part of the fun is in getting a great value