Perhaps, but discussing profitability of AWS in gross margin terms is somewhat pointless. At 100%, that means not a single cost of operating the business has been accounted for. No computers, no engineers, no data centers, no electricity, nothing. It's a meaningless number.
I'm not suggesting the business is not profitable, by all accounts it is, but to understand how it's benefiting the company as a whole, you need to look at the operating line.
Yes, gross margin is (revenue - COGS) / revenue. But per your parent comment, Amazon is not accounting for their AWS costs in COGS. Instead, it is primarily included in the technology and content expense line, which is below the gross margin.
If gross margin = 100%, then by definition COGS = 0. Thus, gross margin is a meaningless number in this case.
I'm not suggesting the business is not profitable, by all accounts it is, but to understand how it's benefiting the company as a whole, you need to look at the operating line.