AWS margin is only relevant if you can be as Efficent as Amazon if you don't have 24/7 need for 100% of your servers then Amazon is likely to be more Efficent internally. It's also highly negotiable at scale. Do 10k per month and you get standard rates, do 200k and you get a little leverage. Do 2M per month and it can be a level playing field.
Cost savings start (moving to your own hardware) at $50K/month spend with AWS. I'd imagine the cost savings are enormous at $2MM/month, although I'll need to dig my spreadsheet out to know for sure.
I doubt you can get accurate numbers for 2MM/month accounts without actually having a 2MM/month account to shop around with. Though if you have real numbers I would love to see them.
