Your scenario also assumes that all of their other related business expenses stay the same, which they will not. The company they purchase from will increase their prices to pay for the delivery truck drivers, OR mom and pop will now have to go and pick up supplies. either way costs go up. Every other cost to them will increase as well to pay for their upstream products.

The scenario i was thinking was along the lines of :
Mom and pop sit down and do the math and realize they can not afford a $100,000+ a year payroll going out the door. So mom and pop fire the employees and instead have all family, kids, etc, working the business. AS a business owner they do not have to be on payroll so they avoid it all together and can possibly keep more of the profits within the family. A side effect though is that they are unlikely paying into SSI, workmans comp and other payroll related expenses, so if something goes wrong, its "BOOM" !