Yesteryears' expensive speakers compared to modern moderately expensive speakers

For the purpose of this discussion, let’s assume that ...
Yesteryears’ -- 10 -15 years old
Expensive speakers -- $25,000+
Moderately expensive speakers -- $8,000 -- 12,000

I often wonder if it’s worth paying 50% of the original retail price for older speakers that were considered state-of-the-art and flagship during their day. So let’s say an expensive Sonus Faber was around $30,000 in 2005. The seller is asking for $10,000 in 2018. Is it worth paying the asking price, or is one better off buying, say an Olympica III, brand new for about $13-14k (maybe less with dealer discounts)?

I feel that due to trickle-down effects and manufacturing advances and efficiencies, the modern speakers are as good, if not better, than speakers that were twice or thrice the price ten to fifteen years ago. Is this a valid assertion? Or do you guys feel that speaker technology really has not advanced to that extent? In other words, is a flagship speaker worth $30k a decade ago still going to outperform a new one at half its price?

The reason I’m asking is that I am going to save some $$$ this year to buy a speaker in the range of $8000-12,000 in about 6 - 7 months. Since it’s a pretty substantial amount (for me), I am planning to do as much research and auditioning in the next few months. So might as well get started now. Given that it is really difficult to audition used speakers -- not that it’s easy to audition new ones, but at least you can if you try, should I just strike used ones (ones that were uber expensive a few years ago but more affordable now) off of my list and just focus on new?

P.S. -- I’m just using Sonus Faber to illustrate my point, otherwise, I’m very open to anything that is in that price range. I am purposely not turning this into a discussion on what I like, room size, music preferences, etc just yet since I want to stay focused on the topic -- yesteryears’ expensive speakers vs not-so-expensive modern ones.

P.S -- I understand that Tekton is going to render all other speakers obsolete in due time, and I respect the opinions of those who agree with the assertions, but please understand that it is not going to be on my list. Period. I will really appreciate if we don’t turn this thread into a Tekton battleground.