depends on the hide, for the thickness. I have some very nice buffalo that I've made several bags of different styles and sizes... about 5 oz. I like 7-8 oz sides from cow. A good grade of carving leather. Not much on splits, although I just finished a give away bag from some 3-4 oz split.
When you have some sources lined up (and there are lots out there), don't be afraid to ask for a sample piece or pieces, especially if you are about to spend upwards of $150 for a cut. The larger the piece, the more readily the seller might consider sending you a sample. It is appropriate to pay shipping on a free sample