In your neck of the woods (not that far from me), I'd say $400ish for a stamped. If it is milled, I'd say add $50 to $100 more to that (depends on the buyer). Some folks really go for the MAK's. I think fetching that much money for them is a little high, but they do occasionally bring it.
I own a stamped MAK90 and love it. I only paid $250 NIB about a year ago. But, that was a really good deal.
If I were buying it, I'd only be willing to go around $375. If I were selling it, I'd adjust that price as I mentioned above. It never hurts to ask a little high and come down. You rarely get the chance to raise your price.
A little factor that might throw a wrench in the pricing scheme I've offered is if it is NOT a Straight cut receiver. You can figure that out by removing the butt-stock. Most anyone that knows about MAK90's will probably ask about that feature. The only real problem that creates is if someone wants to convert it back to the original Pistol Grip configuration. If it is not a Straight cut receiver, then you are very limted to butt-stock choice.
I'm sure others can also offer some advice and opinions. But you have a good piece and shouldn't have that much problem finding a buyer.
DK