Why are movers not paid much over minimum wage? That is terrible, but I am sorry, I wouldn't fork out an extra $320 to cover what the company isn't paying them. Moving is expensive enough and if the company is that greedy to undercut their workers, then appropriate compensation is a problem between the workers and the company and not the customer's responsibility to take care of.
Walmart pays crappy wages ($6.50/hr when I worked there 3 yrs ago), even to the guys that unload the trucks. Should they get tips too?
Tipping is getting out of hand, especially when prices aren't reduced to compensate for the expectation of a tip.