I’ve experienced this and also read reports of it with GoDaddy. But I cannot say the same for Namecheap - I’ve searched for several domain names multiple times through Namecheap and never noticed a price increase (outside of a sale ending and/or the search being multiple weeks later, at which point it makes sense). I’ve also never seen any detailed reports of this happening with Namecheap, and if I’ve seen any at all, I can’t remember them. I have occasionally searched for a domain name that was later unavailable, but that happens infrequently enough that I doubt it’s due to Namecheap doing something nefarious.