I don't think extra practice should equate to extra money. Why should it? If I choose to attend my gym 7 days a week should I pay more? If I choose to attend my martial art school every day they have class why should I pay more?
Of course you should, because you're using up more of the instructor's time. And, if you take showers after every class, then you're using up more of the facilities.
A weight-lifting gym may be different, because there's no instructor. Or, to put it another way, if you had a personal trainer, and you used him more often, shouldn't you pay him more?