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.
It really depends on what it is. If it’s something I love, it depends on what I can afford. I paid $500 for a first edition of The Hitchhiker’s Guide with the Capricorn 1 ad on the back. And I paid quite a bit for an American first edition copy of The Hobbit that I used in place of a ring to propose to my now wife. But most of my books are pretty cheap.
I did manage to find a first print/edition copy of The Shining for $1 at a library sale years ago…that was a cool find.