You could be right, but if they hate longer bookings that much why don't they just not list them instead of putting a price that obviously no-one is going to pay?
The one I don't quite get is when they charge the same for a half hour as for an hour. I get why you would make a half hour almost as expensive (or the hour almost as cheap, depending on how you look at it), as it makes people think 'well, might as well just spend the extra amount and get a full hour'; you're giving the illusion of a good deal. But by charging the same for both, I don't really get the thinking there.