I may regret this, but i spent almost $100 on Harvest Moon SNES in PAL region. Horribly rare, i've really been wanting it. That, and the N64 version are the best harvest moon games. More friends of Mineral Town is probably the best gameboy game - but it takes forever for anything to happen. I don't know what's so great about Harvest Moon, it's addictive. but whatever you do, dont play it's a wonderful life, it'll ruin everything.
But the most wasteful money i've spent on a game is FFVII. I mean, i never played the game but i spend 80 at some place online because they seemed legit, but after 3 hrs or so the game cant load anymore. It took me almost a month to get there because i was very unmotivated about playing it, so they wont give me a refund and say to get it professionally cleaned, which is what they advertised doing on their site before i bought it. Then i buy a new copy and have 2 FFVII games... wasteful... So far i've had it for 4 months and have played less than 20 hours, i sure know how to pace myself