I always assumed it was a side source of profit -- rich tourists and businessmen. If there's a price listed, I never thought of it as inappropriate, especially given the markup.

I think if my income was 2x what it was at one point, I would have taken a hotel robe under the listed price. I've had really mixed experiences buying robes at stores and on-line. You can't tell how well they'll work wet. Hotels sometimes have really nice ones, with the upside you can try them out straight out of the shower, and see how they work.

Downside is the markup.