Checking Amazon...
MMZ1 - $8ish
MMZ2 - $6ish
MMZ3 - $7ish
MMZ4 - $9ish
MMZC - $25ish
Collection is cheaper if you want all 4, but if you only want a couple, then getting the gba carts is cheaper. I imagine these are cart only, though, so with Forte's offers you're essentially only paying a couple more bucks to get the box and manual.