This has been repeated ad nauseum, but labor costs are such a small percentage of business operation that it's barely even worth considering. Wal Mart barely has any employees working at each site for how large they are. It's been studied numerous times, across numerous businesses, and if you recall McDonald's which actually does actually employee a lot of labor relative to other businesses, would barely have to raise the cost of their Big Mac a few cents to pay for a $15 minimum wage.
I don't understand why people still defend the shitty practices of big business, it's mind boggling. But I also tend to find that people who are against a minimum wage increase are the same people who make a few dollars above minimum wage, so they feel that an increase would negate all the "hard work" they did to get to where they are (basically two feet past the starting line).