The main factor is the market for this unused CPU time, a bid of 20% could be vastly different on each service. The GCE pricing model in a way has a sort of ste

The main factor is the market for this unused CPU time, a bid of 20% could be vastly different on each service. The GCE pricing model in a way has a sort of step function applied to the pricing, whereas AWS you can bid however you like, how this effects consumer usage I would guess is higher cost on AWS due to perceived competition. This is all assuming the CPU time on machines is constant.