Arun Sirpal describes Azure elastic database pools:
The key to using elastic database pools is that you must understand the characteristics of the databases involved and their utilisation patterns, if you do not understand this then the idea of using an elastic database pool may cause problems.
The maximum amount my pool has is 100 eDTUs, I know for a fact that the S2 databases will not be used at the same time, the other S0 databases might be used at the same time at the most 3 of them at the same time. Basically what I am saying here is that I know that when the databases concurrently peak I know that it will not go beyond the 100 eDTU limit.
One thing that Arun does not mention is the relative ease of interconnecting databases within a pool, so even if it doesn’t end up being cheaper on net, that might be a benefit worth having.