Right.
Also, if we sell the room and then run out of gold completely - creatures will leave forever. With basic rooms on map, at least lv1 creatures will keep coming and going.
So, what do you propose? Not sell any rooms? Sell in special conditions?
This is more complicated. Anyway, I'll try to adjust the algorithm to match the decisions we'll make here. Recently I made a big change there too - given more focus to training.