>I’m really confused how you communicate with it? That seems like the most (expensive?) and technically difficult part.

Not really. They typically use standard amatuer radio frequencies and protocols. Making space to ground contacts is doable with a handheld radio and directional antenna. Main limitation is low data rates (dialup or worse) and low coverage (you'll probably only get 1-2 passes a day from a single ground station). A decent semi-permament ground station can be built from off the shelf parts at a fraction of the cost of the overall satellite.