What do $2500 speaker cables sound like?

Your best bet is finding loaner cables or purchasing with a no hassle return policy.

Otherwise it's a yes,no and maybe Merry go round.

I have 3 speaker cables.

1) Benchmark cables with SpeakON connector ($150)
2) Audience Conductor SE (I think $1K)
3) Audience FrontRow with SpeakON connectors (around $3.5K)

The first 2 are very good for the price and when I use them I do not feel like I am missing out.

However, when I put in the FrontRow in the floor standing system I heard more detail and more clarity. Improvement on an already good sound.

Now the place where I really notice the greatness of the FrontRow wire is when I put them with my Benchmark AHB2 amps to drive my RAAL SR1a headphones. With the other cables I noticed a bit of hardness and had some fatigue via the headphones. With the FrontRow the hardness went away as did the fatigue. So I have crazy expensive speaker cable for my headphones. With my floor standers it was not needed as much as with the headphones.

I cannot think of anything as more revealing than the RAAL SR1a so it makes sense that the FrontRow made a difference.

"...What do $2500 speaker cables sound like?..."

Cables are qualified by their sound qualities not their price. If you think $2500 is a lot of money for a cable you probably aren't going to buy it, so it's a moot point anyway. 

Whatever happened to tone controls? That solves any problem you have

Will sound FAR better in your system as your brain won't let you are a complete fool.
Not a joke .