If you can wait a couple of days to get them talk to Hog Sniper (IP here I believe) from High Rock Outfitters in Hanover, PA. He has great prices and can get stuff in pretty quick. Great to work with. Drop him a PM.
MSRP. Was just there a bit ago. Gen3 30rd were 14.95. 17.95 for the windowed version. They also have a nice variety of other common mags such as: AK, glock , mini-14, pistol such as kimber . Also had bunch of various magpie parts, holsters a plenty. They have a good gun store and transfer through Ricks in Conowingo, although I haven’t bought from them myself.