OK, I'm missing where it said it was a slant cut? Even if it is a slant cut, the ironwooddesigns stock set are $88-$102 dollars depending on which stock set you get. If you use 2 mag compliance parts in the mags you will be using in the rifle you can get it completed for about $122.00 additional.
$350.00 + $112.00(at the most) $462.00 max for a milled slant cut Mak 90. Actually depending on if it is stamped and straight back receiver you could get by with a cheaper ironwood stockset. $450.00 total.
If it is a stamped receiver I believe you can get a Ironwood Designs stock set from
Volunter Ordnance Works for $60.00, $20.00 for plenty of US mag followers and baseplates and you have all of your compliance parts.
Total price $430.00.
For a different point of view, go ask the same question over at
The AK Forum I believe the majority will give you the opinion that it is a good deal. You aren't going to find too many NIB AK's of any kind at that price. It is better deal than a Romanian rifle at that price. NIB SAR's go for over $400.00 now, they originally sold for $289.00 or so.
Bachelor_of_Science is a dealer, I would take his advise on the value of a rifle when he is not even the one selling it and standing to gain on the deal.