best deal: got an A500 from dad in June 1988, and since I was 16 and had no financial means at all, I got it for free
other deals: hardware bootswitch I got for free from a guy who bought it, failed to install it properly, made his Amiga braindead; so asked me to see if I could fix: a CIA had a bent pin not making contact anymore do to badly socketed bootswitch. So fixed it, but guy got so scared about bootswitch he did not want it anymore so gave it for free, still is in my A500 today!
Action Replay MK3 for free - but never used it (still in my cellar)
Bridgeboard A2286 for free - but never used it (don't even know where it is now)
A3100 or something like that SCSI tapestreamer with several tapes which turned out to be a full backup of the Boondocks BBS ! 2 tapes were unreadable tho... - once all tapes were backed up, gave it away for free to a US guy based on military base in Germany
Baracuda 9GB SCSI HD I bought for about 50 euros in 1997 for my A4000/040 (was one of the best HDs back in the nineties)
a twat from a Amiga computer shop in Genk (Belgium) where I bought end of 1994 a 2nd HD FDD for my A4000, was already overpriced (near 200 euro I believe), the guy could not install it properly (due to wrong FDD cable assembly causing leds of both drives to light up when DF0 was active) and still guy charged me about 20 euros for 'correct installation' which took 5 minutes, pretending the led issue was 'normal' and I had to live with it.
other bad deal: USB1.1 + ethernet card for A4000 2 years ago, new from shop,was nearly 250 euro, too silly price considering how obsolete the hardware was. It did work thought; albeit very slow and cumbersome to configure.