Does this take into account the cost of commercial ink vs consumer ink? I don't know but I would bet the ink used on a drink cup is cheap.

At best, I think this is misplaced concern. At worst, I think this is a cash making scheme by guilting people into buying their design services which they advertise at the bottom of the page.

EDIT: I thought about it some more and the cost savings don't take into account the costs of redesigning your logo, retooling your printers or replacing your storefront signs. In either the ecological or economical sense.