Well, they also tapped up Moyes and made him run down his contract at Everton so they didn't have to pay Everton a year of his contract either (?3m?). So it seems even for much smaller figures, the Glazers arn't against this sort of vaguely distateful underhand sort of business.
Hiring him for 10 months then trying to increase the already immense pressure on him so he just quits his job is pretty horrible mind you, Moyes seems like a nice guy with integrity, and I can't imagine that dilemma of constant pressure yesterday on top of a horrible season would have been easy.
Moyes was leaving anyway, that was his last year (he was free in the summer), so there wasnt actually anything to pay.. In fact Moyes was going to take a break after Everton (perhaps burnt out?) But in his position, would you turn it down?