I also don't think fender has done a Johnny Winter signature copy Agent, the cheapest signature copy as far as I know is around the $600 mark so the guy got a good deal if he got one for that price, Sam Ash might have had a special to off load one but that's a good reduction, looks like a good deal at face value but probably worth finding out what it really is and checking it out if possible.
Here's a link to most of Johnny Winter's guitars and it's great just to hear his name mentioned he's brilliant.
Guitars and Gear
You don't stop laughing when you grow old; you grow old when you stop laughing.