Technology in speakers....

So... I am curious as to your opinions of the impact of technology and progress with regards to the design and manufacture of speakers. For example, how would a highly regarded and top rated [originally] $15,000 speaker of 10 years ago compare to a modern speaker? Would it compare to a well designed $10,000 speaker today or would it take $20,000+ to compare??? Or has there not been that much change and the value basis is about the same?

I know, it’s a broad conversational topic with no parameters. Just curious as to people’s thoughts on this. Considering that a pre-owned older speaker could be 40% of its original retail price - would you consider money better spent on a preowned speaker which might offer a superior value vs retail price or on a newer speaker that would have to be half the retail price of the comparable speaker’s original price? Assuming of course that one doesn’t mind pre-owned with some scratches etc. 

In short, if you had say $7k to spend would you pick a 10 yrs $15-18k speaker or a newer $7-10k speaker? Finally, would the answer change if you are planning to keep and use this speaker for a very long time?

Thanks for any thoughts with this.