Every single node in a blueprint has a cost that is probably 10x the cost of a simple function call in C++. A macro that contains 10 nodes, would be 100x the cost of a simple function call.
Whether this cost matters, is a different question. If you call it once per ant per step in an ant hill simulation, it will absolutely be. If you call it once per player per tick in a single-player game, it’s unlikely it will matter at all.