<i>Critically, no matter what your bid is, you never pay more than the spot price which is “The current market price of a Spot instance per hour.” With this in mind you don’t have to guess what to bid and since your bid matches the on-demand price, your instance will never be terminated early due to the price exceeding your bid.</i><p>This isn't accurate, the spot price can absolutely be higher than on demand pricing and isn't a reliable method to prevent your instance from being terminated.