Can't say I blame the creator of this if people are profiting, even to minuscule amounts, off his hard work.
The dude probably isn't making a dime off these, and has likely put hundreds is not thousands of hours into the code and hardware, so I don't begrudge him griping to ebay (assuming it was him that did the griping) if people are flogging off his hard work and making even minor profits while he's likely having a hard time even breaking even.