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 min

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. 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.