You'd be surprised. A few years back a member whose ID I could never spell (Chimensche?) did an anniversary shave video and it was an extremely popular thread for several weeks.
I would definitely watch! I have been honing on JNAT for over a year, but I still consider myself in the 'learning' phase for sure. You can learn a lot by just by watching!
I recall seeing someone with a sword sharpening/jnat selling site that looked like it hadn't been updated in about five years list that they were selling a bench sized koma (I wanna say a bit shy of a kilo) for like $1000 but that they'd only sell it if they felt it was going to someone who knew how to use it or some such business.
I remember on a knife forum a while back someone (a sword polisher if I recall) was selling a number of Koma pieces.. both small stones and Toishi size. At the time I was not interested in investing so much but he had a few he was asking near $4000 for some of the biggest pieces. I'd be curious to know just what kind of sizes they were.. I should have asked for pictures!
4k for a brick of Koma isn't all that surprising if it's significantly over 1kg.
I've been offered 700g-ish pieces for 1k+. Depends on the stone, who's buying/selling, etc.