INMHO any company that sells solution completely relying on managed cloud services by these 3 has 2 problems to deal with: - What happens to the cost of these

INMHO any company that sells solution completely relying on managed cloud services by these 3 has 2 problems to deal with: - What happens to the cost of these services when company scales out? - Whats preventing AWS, AZURE or GCP from copying the stack and selling a new "managed service" which does what you did in the first place? Seriously, I would like to know? Do people take these into accounts before relying on AWS, Azure or GCP completely?