Hey Marie :-) Yes, it's certainly a lot cheaper in the long run. The only hassle i had was making sure i got food grade and not technical grade Mag chloride. It is the best quality available aside from digging out crystals from that famous lake, which i can't rememeber right now ;-)
Interesting to note, the technical info for impurities of the mag from that lake matched the levels i found in food grade mag. chloride so i was happy.