Your entire premise is based on a pair of servers - we're talking about fortune 500s. I'll ignore for a second the fact that $20k/month in server spend for a pair of servers to be database+web is grossly overpriced, even at LIST, which no fortune 500 ever comes close to paying.

All of the "and you don't get all these other services" is just a red herring because, again, we're talking about a fortune 500 that isn't building their services on a pair of servers. They buy racks at a time, at minimum, and unless they're grossly oversizing what they're buying, will have better performance per-dollar all-in, including the people cost and the surrounding infrastructure cost, to say nothing of the egress bandwidth because you know, their customers aren't just other AWS servers...