Welcome to the site StormOSteel.
As to your first question... I'd imagine so, as California and other states cannot order new hi capacity magazines, so there's probably a premium on price.
Second question... They don't change the size of the magazine. They just put a plastic "block" of sorts on the bottom of the follower so that you cannot load more than 10 rounds. Please do not cut that off if you live in a state that does not allow hi cap mags, it amounts to bad joo joo for whoever does it.