Right now it seems $20 is the bottom dollar for unissued/grade 1 mags.
Normally I'd recommend KeepShooting.com but right now they're asking $30 a pop, and Clearview wants $35.
They seem to come in waves and when they do the price creeps up every time. Last batch I bought several years ago $13 for unissued mags was the best price I found. I think that was from Numrich Gun parts on sale. But not grade 1, closer to grade 2 with springs that were showing their age.
Fortunately I had a batch of replacement springs but at $3 a pop I could have just bumped up to unissued/grade 1.
Straight from the source, Czechpoint USA shows 30 round mags for $25 but not in stock.
Right now Numrich has their new factory VZ mags on sale for $20, not bad when their USED VZ mags are still $22.
These surplus mags get pricier every day. I bought a Chinese 5 round AK mag from an online vendor for $8 for a project, back then you couldn't give 'em away. Last month when I decided to pick up a few more, now they're $25 or more.