At the single instance very small scale, it simply doesn't matter all that much. "Our business failed because our infrastructure bill was $400 instead of $150 every month" isn't that common of a story.
Base load can be effectively migrated to AWS, depending upon how it's built / structured. It's hard to lose money on infrastructure by converting worker servers to spot instances or lambda functions, as a for-instance-- but it's VERY easy to lose months of engineering effort in doing so.
Remember as well: done right you're not just buying services from the cloud, but flexibility as well. Resizing on the fly, bursting, duplicating your infrastructure for a test-- these things add value.
A lot of teams rent space from places like OVH or Hetzner because the raw power is so much cheaper, and they already have the talent and tools to scale and manage a computing fleet (people like to think it's harder than it actually is).
Those marginal gains could potentially pay for a dozen engineers...