There are periodic threads on this subject, always expressing amazement.
About ten years ago I flirted with selling digital cameras on ebay. I couldn't believe the prices I was seeing them going for. So, I sold seven or eight of them. Where did I source? Amazon. How hard would it have been for the ebayers to look on Amazon? But they didn't.
Net, after all the costs involved, on cameras around the £100 mark, I typically made £15. If I could have been bothered there was a business there to be had. I chose not to.
People assume they are getting a bargain on ebay and seem not to bother checking elsewhere. More fool them. There's nothing sinister in it, just the fact that there really does seem to be one born every minute.
Vin