Have you ever been bitten by the completionist bug? What game? Have you actually played it?
I'm much better at avoiding the completionist compulsion these days, but I've definitely done my fair share.
Kingdom Death: Monster - $1666 all-in for the second kickstarter. I've only ever played the base game, but I've built a lot of the models. I still get some of the other stuff they release on their store, but definitely not all of it.
Sentinels of the Multiverse: Bought the very first edition of the game direct from Christopher Badell's hands at PAX Prime in 2011. Collected everything up to Oblivaeon and the big black box. Promos, rarities, misprints. Once sold a single card (that I had two of) for $100. I haven't played in years, but I'm not getting rid of it. I have zero interest in the new edition.
Too Many Bones: Went all-in on the Splice & Dice kickstarter, the one with the Trove Chest. Also bought Unbreakable and the extra gearlocs there, though they're still in shrink. I've managed to avoid the need to hunt down promos and things like the pop-up book. I've only played a handful of times. Something to get back to.
Millennium Blades: I own all of it. I've only played once, and it wasn't even my copy.
Clinic: I own all of it, because I like the theme and design. I've never played. The bug still has its teeth in me for this one. I was a bit disappointed to learn that there's going to be another expansion this year.
Lacerda: I'm a sucker for the Lacerda/EagleGryphon deluxe boxes. Just lovely things to own. I've played half of them. I hope one day the CO2 license will revert and we can get an EGG version of that one too.