Where does it end?

When you are not interested any more.

G

Okay, you got a turntable and speaker cables.  Now you need an integrated amplifier and speakers to make it work - the end. 

Never ends just keep spending big bucks as its way cool.

It ends when you get where you want to be...unless something breaks or there is a significant advance. $4000 for speaker wires?
I use one of the best speaker wires available, Kimber 12TC. Since I terminate them myself they cost me $300 including connectors. If I put a sock over them I could pass them off as $10,000 cables in this silly market. 

Back in the early 80s, I was using a modified Dyna-70 and a modified Dyna PAS pre-amp in my main system. They sounded really good. I was toying with the idea of upgrading the pre-amp. At the time Audio Illusions was getting rave reviews. At $1100 it would have been a stretch at the time, but doable. So ... I took the trek down the Coast Highway to Santa Monica to visit Randy Cooley’s "Optimal Enchantment."

After the audition, I told Randy that the Audio Illusion piece sounded pretty much like what I had at home. Randy said, "well, let me demonstrate the Audio Research SP-??. It sounded glorious. When I asked what the price was, he said "$3,500. I looked at Randy in shock and said ... "Are you kidding Randy? Who in their right mind would pay $3,500 for a preamp?" Randy smiled and simply replied ... "Guys like you." Ha! Prophetic words, for sure.

By the way, if you are in Southern California, I encourage you to make an appointment with Randy. A cooler guy doesn’t exist in the business. And ... a true music lover to boot.
https://www.optimalenchantment.com/

To simply answer the OP’s question: It doesn’t.

Frank