For the Amazon FPGA rentals, you are only allowed to pull 85W on the FPGA (nearly nothing), making it very hard to make enough profit to pay for the rental. It is possible, but you won't make anywhere close as to what you can make with a real piece of hardware.
I fully expect it to not even cover the rental, but want to learn from seeing it running and work my way backwards before considering purchasing expensive hardware that I do not have the knowledge to make use of.