Around that certain point you can also talk to AWS or GCP and get very significant discounts. I'm surprised 37signals and AWS didn't find a number that worked for both.
I've seen a few of these deals with other vendors up close, the difference with public pricing is huge if you spend millions per year.
I worked/consulted for several companies who had multimillion per year cloud commits, sometimes with different clouds, and those discounts are not competitive with onprem like at all
I've seen a few of these deals with other vendors up close, the difference with public pricing is huge if you spend millions per year.