PoE can be cheap, but usually never cheaper than non-poe. But if you have a PoE switch and spare ports, its very nice.

The problem comes when you try to design a large network and need random PoE ports on end devices where you can't home-run a cable back.

I have a Unifi Pro XG 48 PoE and I love it, but I still don't use PoE for everything. The cost of a (non unifi) poe device + the cost of using one of those ports always exceeds a simple power adapter on the other side (if possible).

I think about this a lot.