Sound Blaster 16 with IDE port and 3x NEC CDROM drive. Mail ordered from HK for around $800 shipped in 1994, sure it was cool at the time, but $ completely wasted a couple years later (cost only $200 locally) and never really used it that much (pretty useless).
The $600 alarm system the dealer charged for and failed 3 times in 3 years, only to find out that it cost around $120 installed from a small shop.
A bunch of overpriced auto services and questionable quality tires for top prices, only to realize that sells for 50% off with coupons or on tirerack.com
Other than that a $200 RFID badge reader when trying to do a project for a quick buck but never get around to do it, and my partner is completely clueless and can't help.
Then there are a bunch of programming books, computer parts, USB drives, etc that I bought just for discounts and cool factors but useless in real life, total about $200.