@Peltz If you’re patient and know what you’re looking for, Goodwill auctions (filtered for GBA - you can only filter for one system at a time) will reap benefits.
I’ve purchased way too much off there. Not GB/C/A, but one of my most recent purchases was a PS Vita TV which arrived CIB with the twist ties still on the power cable. I bought my Dreamcast there which unexpectedly arrived with sealed copies of NFL 2k and Virtual On. A while back I picked up a Genesis model 1 for parts or repair that only had the PSU port mount broken inside, but otherwise worked fine. I don’t have pics, but also got a GBA SP AGS-101 in good condition - some scratches on the top exterior. Pre pandemic I saw three Switch Lites NIB go for $300 each (multiple bids). Who the F donates new stuff like that to Goodwill? Deals are there if you’re diligent - please people bid on these things so I don’t buy more gaming stuff I don’t need! please! lol