Assuming everything is on the up and up it's a solid trade for you.
Xmen266 = $190
Flash = $235 (avg of 280 and 190)
Total = $425
ASM40 = $350 (avg of 450 and 250)
BA12 = $510
Total = $860
No idea why someone would trade you more than twice the value of your books. Hopefully he's not doing anything shady.
THIS.
However, I have had people trade for more b/c they either had doubles, etc. and didn't want to bother/hassle to sell themselves, but "giving up" double value (or more) seems excessive, especially when the books being traded for are readily available online.
...If it is on the up and up and it works out congrats in advance.
Thanks he said he liked x-men and we kinda hit it off talking about girls and he said he liked my honesty. So it sounds great if you put it in numbers like that and I have yet to see if he goes by his word like he says he does though I did a check on him and nothing seemed suspicious.