Or even better $10 for n tokens, $20 for n * 2,5 tokens, $30 for n*3 tokens or something to that effect. Charge me monthly to to up but not if I have more than

Or even better $10 for n tokens, $20 for n * 2,5 tokens, $30 for n*3 tokens or something to that effect. Charge me monthly to to up but not if I have more than m unspent tokens.