It would be amusing to run this on a regular desktop computer or even a moderately nice laptop (with a fan - give it a chance!) and see how it does. 650GB will stream in quite quickly from any decent NVMe device, and those 8-16 cores might well be considerably faster than whatever cores the cloud machines are giving you.

S3 is an amazingly engineered product, operates at truly impressive scale, is quite reasonably priced if you think of it as warm-to-very-cold storage with excellent durability properties, and has performance that barely holds a candle to any decent modern local storage device.