I see nothing wrong with someone selling these, whether they came from an estate sale, or were made specifically for sale on eBay.
What I DO wonder about is whether anyone who is either too lazy or too incompetent with electrical stuff to make their own, has any business getting anywhere near to old radios, with the intention to repair them.
To test a radio out just to see if it works, okay... but if it doesn't work, then you'd better be competent to fix it. Otherwise, take it to someone who is. They will have a dim-bulb tester, or be able to make one. It has to be one of the easiest things to make, in this whole hobby. If you can't manage it, you probably can't manage a decent repair job, either.
I'm not sure what a fair price for one of these would be, but I wish the seller good luck with the sale.