The Maadi is worth maybe $300 tops, NIB. If its used and he's a good friend......use your judgement.
As far as the mags go, the 40 rounder is probably worth 10 bucks.
The rest are anywhere from 5-10 bucks a piece.
The dust cover mount, you can buy for i think around 15-25 dollars. (But is worthless in my opinion, as it doesnt hold zero)
As a Package I'd say.....$300-$320
Good Luck