We play with a base point being a dime or a quarter. Note also that the function from fan to points is subject to house rules, it's not always p(f) = 2^f (I've seen rules for example that start to "level off" the payout at higher fan values).

I'd add the note that the whole strategy of mahjong really only gets interesting when you play repeated hands (a full game has at least 16 hands, with each player acting as the dealer once per prevailing wind) and when you're gambling (or otherwise tracking points). Most house rules also enforce a minimum fan value for a winning hand, banning the "chicken hand" which wins but scores no points. We play with a 2 fan minimum. If you just play for mahjong (i.e. a a hand that "wins" the round regardless of score), the game is a pretty uninteresting game of luck, and you're not incentivized to gun for the higher scoring hands.