You'd be surprised at the complexity involved moving 1-5MM USD across borders, even those without capital controls. And there is definitely a limit on global throughput of dollar movement, which is roughly the slowest processing rate of all the bank compliance divisions involved in the transfer. For complex cross-border transfers there may be more than 2 banks involved.

Greater amounts still would attract even more scrutiny due to AML and KYC regulations in most jurisdictions.

If you're dealing with capital controls, which many large economies now have, the complexity is exponentially higher. You're also assuming that telecommunications networks, physical infrastructure, particularly power, are in good working order when you want to do the transfer. That may be the case 99.99% of the time, but the edge case should also be a consideration.