a pair? if i'm not mistaken, thats only two.
if he has a set (4) of the demonya that has the things he stated i suggest you do this:
1.check on the internet the prices of the ADR Demonyas from at least 3 sites. see how much the whole package (tires and rims) cost.
2.check out the rims he's selling you. make a note of ll the damages and calculate whether $400 is a good price compared to the other prices of brand new rims.
IMO i'd save the $400 that you plan on using and save up more money and get new rims.