The "charge more" advice I've seen, e.g. from patio11, seems to be aimed at charging _new clients_ or for _new contracts_, and in almost all cases has the caveat that one should almost never up-charge existing clients for the same service that they already have. You can add a new higher-price service tier, or grandfather them in _forever_ at the original price, etc, or quote them a larger price for the next consultation ("My fee is now X"), but in every case they have the option to walk away.