Purchasing MySQL Support generally encompasses supporting MySQL Community Binaries as well, not just MySQL Enterprise. Depending on the type of problem you have, the answer may well be install MySQL Enterprise. I'd like to read the fine print to see if this holds also for AWS support, or whether a Enterprise only restriction will be a requirement. As you pointed out the pricing model will also require review. Talk to one sales person in which you have an Active/Passive failover environment, and you need 2 licenses even though only one may be technically running, and only one should be necessary. With the level of AWS virtualization you will be running more MySQL instances on less powered machines, and therefore your numbers of services increases and cost of support matches.