Not only that, but MacStadium lets you run multiple VMs on a single Mac at no extra cost. Amazon's offering is seriously underwhelming
To the hobbiest market, yes. But large companies, at which this seem to be aimed, work with names they know, not names they don't.
The company I work for would pay more to use Amazon than MacStadium for equivalent products. That's just how corporate bureaucracy works. It shouldn't, but it almost always does.