That is just about the cost of the whole system! I knew there had to be a way to refill them. And sure enough there is! You do however have to be careful because the cap is very fragile and you have to make sure not to mess with the little hole where the soap connects to the system otherwise it will leak.
Simply slide a butter knife slowly under the cap. The once the knife is under there you slide it over to the other side and it will pop off. Make sense?