Reading. Bear with me…you start by getting a cheap physical or digital copy of the book. Then you fall in love with the book/author. Then you have to buy all the books by that author…but not the cheap editions…the fancy editions! You need to display these babies! And oh! They sell cool collectors items that would be perfect for the book shelf! Rinse and repeat for so…so many books. Sigh.
You sound like my friend. She owns multiple editions of the same books because there was a fancy cover but then the books had matching covers with related books but oh look they made an illustrated edition!
My wife and I have a room with an entire wall full of books, more in numerous bookcases around the house, and a couple boxes of books that aren't on shelves. They're mostly bought second hand on eBay, dirt cheap. Reading is cheap. Collecting pristine/fancy copies is expensive.
You start at the library... then you read a series they only have the first 2 of and fall in love.
So you need to buy the third one somewhere... then you have a choice to make, do you really buy JUST the third of a series? May as well just buy the box set...