I bought my K46 from CSS last year, and there isn't a better way to buy an RR imho. I certainly wouldn't have done so otherwise, and if for some reason I wanted another I would do it again.
As Dylan said, most students aren't riding anywhere near the bike's limit. Most of those miles are by midlevel track riders who are out there practicing specific drills rather than going for all out lap times. I did think about the mileage and use of the bikes, but having been to CSS and seing the riders, the condition of the bikes I rode, and seeing/talking to the mechanic made me comfortable with it. Moresoe than buying a used bike privately since you can talk to the mechanic, who is a good guy too.
My bike had just over 20k when I bought it and runs flawlessly. I've put about 1300 on it, all track since I got it as a dedicated track bike. I intended to have ridden a lot more this year, but track days where shutdown for a while due to the virus.