To cut costs on soap refills by 50% to 66% :
~ Take your emptied soap dispenser.
~ Fill 1/3 to 1/2 with soap.
~ Add water.
~ You've got soap.
One of the things I like about diluted hand soap is that you can start washing and scrubbing your hands before turning on the faucet, thus saving water. With full-concentration soap, you have to wet your hands first to get the soap to lather. This soap is already "wet".
For foaming soap dispensers, lean towards 1/3 soap.