However, how much they charge for it gives a general idea, since they are paying for the power.

That could or could not be correct. We don't know their bill of materials. Probably some people can estimate it better for Intel. I understand the ARM stuff is AWS proprietary, so I would be surprised is any figures are public. Besides the costs are unkown the margins could be very different. AWS might be willing to pay a high investment to get more independent of Intel in the long term.

I worked at a big corporation in the mobile space before. They were willing to pay a high investment to get more independent of their single ARM SoC supplier. (It failed because Intel could not deliver in the end.)