Not sure if the comparison to EVO is fair The EVO is a "full size" AEG internally and not an AEP.
The EVO mags are 16gbp per midcap. That's not really that expensive. They should be more though lol.
500rnds with EVO: 106gbp
500rnds with M4 AEG (PTS mag): 90gbp
500 rnds with M4 AEG (MAG midcap): 30gbp
500rnds with M4 NGRS: 143gbp
2250rnds in 5 x g&g 450rnd highcap: 90gbp
500rnds with TM MP7 GBB: 437,5gbp
Prices do vary, and EVO is not the cheapest, but i think only GBB really stands out.
I mean yeah 15 mags like i have for my EVO is not free, but that is a lot of firepower really