To be fair, the one you listed on eBay wasn't a TR412X40 either. It also doesn't show us the actual price it sold for only the asking price. I've not looked on eBay for them, but I've seen numerous ones at gun shows for sale as well as a few on local forums. They are out there, and I've not seen any for anywhere near $300. In fact, I've never seen one over $200 and the ones over $150 have sat there and not sold. The ones I've seen bring $150 have had the original box and been in new condition.
I think you are way overvaluing a Tasco. When people talk about the old Japanese Tasco's being worth more, they mean compared to the current crop of $75 Tasco's. Not that they are worth more than a Burris or Leupold of that same power as they aren't. That said, if he can find someone to offer him over $300 I think he should take it in a heartbeat.