An Ibanez RG570 is a pretty decent guitar. I have about 5 or 6 of them laying around here.
Depending on what year it is, and what condition it is in, I would say that it would easily fetch around $400 or so.
In a trade for a '92 Jackson DK2, which I'm guessing the market value to be around $500-$600, again, depending on condition. I don't think you'd need to be putting that much cash into it.
Give him the $100 offer, but I really wouldn't pony up more than $200.