However, I also think it's a sign of failure in planning and architecture foresight if it's too expensive to move away from a particular cloud provider.
The sunk cost fallacy is when you (irrationally) decide to stick with what you're doing purely because you've already spent a lot of resources on it. It doesn't apply when you've done an economic analysis and found out it doesn't make sense to swap.
There are plenty of cases where it just wouldn't make sense to switch after looking at the costs, opportunity costs, etc. For example, if his site makes him $10 a month, outages cost him $1 a month that could be mitigated by moving, and it would cost $1000 of labor to swap providers. (Depends on interest rates.)
Perhaps it was originally a failure to not have a plan to easily move from a provider, but it doesn't seem unreasonable to me that right now it may cost too many hours of work to justify the move.
It's not as though it would be impossible; our integration with AWS isn't that deep, it's not as though we use DynamoDB for our core data store or anything like that. But even migrating from one traditional datacenter to another isn't easy from an operational point of view.
There needs to be a clear financial win. Even taking into account the failures we've seen so far, I don't see a compelling reason to leave AWS.
There are plenty of cases where it just wouldn't make sense to switch after looking at the costs, opportunity costs, etc. For example, if his site makes him $10 a month, outages cost him $1 a month that could be mitigated by moving, and it would cost $1000 of labor to swap providers. (Depends on interest rates.)
Perhaps it was originally a failure to not have a plan to easily move from a provider, but it doesn't seem unreasonable to me that right now it may cost too many hours of work to justify the move.