I've been selling mags on the EE for months at about the same price as 44mag.com. So have other people. You can get 10 D&H black/grey 30rnd mags even with magpul anti-tilt followers for like $11 and $13.00 each respectively.
ETA: I also have to say that I find it insane that you are BUILDING A COMPLETE RIFLE and you are bitching about the costs of mags and you're even electing to wait on a specific vendor?!? Mags are like the most miniscule thing in an AR15 build and there are hundreds of vendors that sell them, usually all within a single dollar of each other. Christ man, that's just fuckin stupid...
Ahh shit just noticed you were saying 10 rounder mags. I haven't checked around but I guess they could possibly be hard to find right now at a good price or something.
- rem