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 get hardcovers of series I really like, otherwise it’s usually paperback.
But I did spend AU$120 to get the last book in a trilogy that had been eluding me. The first two books I got for like $20. Couldn’t find the third anywhere for years. The only option was this omnibus edition with all 3 books, at Au$120 on Amazon.
Glad I got it, I can still see it on Amazon but now for around $300. It’s not a well known trilogy, the Deepwater trilogy by NZ author Ken Catran. I read those books so much as a kid that I just had to read them all again as an adult.