The only times I've ever bought something through eBay was for stuff I simply could not find anywhere else at even close to a reasonable price. Here's my short list.
- SunVideo SBus frame capture board - This was discontinued back in 1995. I wanted to play with video conferencing on my workstation. Sun had some old cards in stock but wanted $800 each for them. I got one off eBay for $53. You can read about my setup here if you're interested.
- Speakerbox for my cellphone's carkit - I broke the one I had and then broke it even more trying to repair it. A new one was around $120 from Nokia. I found one on eBay for $12 because some guy bought a truck and this thing was in it but he didn't have a Nokia phone to use it with.
- Fantray and controller board for an old Sun SPARC StorageArray model 110 - After a power failure, my 30-drive SSA 110 which I originally found in my old lab at work being used as a doorstop was faulting and refusing to boot up properly. It seemed like the fantray which I had already repaired twice before with new fans was the culprit. Unfortunately, I was out of town and I tried diagnosing it over the phone with my wife. When I got home, and tested the tray, it tested fine but was still showing a fault. I then began to suspect the controller board. I called up Sun as well as some resellers to see what they had in stock. This thing hadn't been made since the mid-1990s yet I was getting price quotes of around $700 to $1000 for a controller board with the serial optical fibrechannel interfaces. I hunted around on eBay and came across someone selling some old SSA supplies for $50. He was offerring both a fantray and controller board (minus the GBICs but I had those). I placed my bid and won the auction. However, that night, I decided to swap the power supply on the SSA with a spare one I had lying about and to my surprise, all the fans spun up and everything was happy. Still I don't regret the eBay purchase as those parts are obviously hard to come by and now I have spares for if/when the ones I have in service decide to die.