Possible to Use Material Instance Constants instead of Dynamics?

The documentation says that MICs can only change scalars and vectors, and back in UDK, we could do the same thing with MICs. I’d rather not incur the cost of a MID if I can use a MIC instead. My engineers are not happy with the number of material pokes I want to do in blueprints.

Seems weird that MICs could be changed at run-time in Unreal 3, but not in Unreal 4, and instead, we got these costly MIDs.

What cost of the MID you are talking about? CPU, GPU, memory?