the regulator is in the mag otherwise the gun would just gone "plop". maybe my shots fps is due to the low temp in here.
for the fill per shot it's roughly the same as the co2 mags (havent tested it but seems to be very close to the co2 one)
and for the price difference well they are 39$ on ehobby and the co2 mags are 40$ here but with the ehobby shipping and currency exchange the maruzen mag is becoming more expensive but worth it.
http://shop.ehobbyasia.com/maruzen-m...-m11-50rd.html