I like to get my hands on the cheapest edition I can in the best condition at that price. If the words in the book are the same as a more expensive one, I’m getting a better value, in my opinion. Then if it’s a story that becomes really important to me I might consider upgrading to a “nicer” or collectors version, and keep the old ones as lender books.
I only buy physical books. I just like not having a screen. I’ll usually stop at $25 per book unless another edition has a better cover art for a few extra dollars or the only edition I can find is hardback.