Buy them while you can at that price they have gone up since the supply is drying up.
Not sure what they have .50 cans for, but there's a surplus shop in Bloomington that has .30 cal cans for either $5 or $7 each, good condition, dad called me when he found them and had him grab me three a month or three back... Said they had a whole pallet, and apparently good prices on most of their other stuff.
Need to find it and check it out myself...