All those things are true. It still doesn’t sound like 1000+ engineers at 350k/yr.

What actually happens in a startup is you encounter these problems one at a time as they arise.

It's still possible. Have the product and hire other people for these things.

Use stripe, cloudflare, whatever the legal equivalent of these stuff, S3.

Yes they might take most potential profit, but you'll also not have a huge payroll.