I believe the free tier has higher* response times.
Also as far as I know once you get to something like 100Tb a month they will ask you or require you to upgrade. But thats still ridiculously high, the same would cost $12k on AWS.
The higher tiers have hard guarantees on response times and level of support you'll get.
In my experience customers do a great job of self-segregating. If you offer "enterprise" as a tier, enterprises will generally pick it, even if the listed benefits are the same as another package. In exchange, they will expect enterprise services -- billing, guaranteed response, etc. No free lunch/get what you pay for.
The only corner case is when an important person at an enterprise customer has a personal account too, or when someone is really being a scrappy startup and trying to run something huge on a personal account due to not having the resources. Usually a good salesperson can handle both of those situations.
Also as far as I know once you get to something like 100Tb a month they will ask you or require you to upgrade. But thats still ridiculously high, the same would cost $12k on AWS.
*Edit: mixed higher and lower