[7rurl]

Can't you add new tiers at any time? You could make parallel $15, $30, $50 and $100 tiers. Also, nobody has actually paid yet, since the money isn't collected until the end of the period. People can change their amount and reward selection at any time before the backing period ends.

I agree with you in theory that kickstarter isn't a place to shop, but in practice it appears that offering 0 marginal cost rewards (e.g. software, videos, early access, media, etc...) at low tiers is a very successful strategy.