Remove the hard-coded dollar values

[tshearouse]

We should know the price. If a user has a discounted membership, that's documented in the member spreadsheet. Instead of a big chain of hard-coded dollar values, move that logic inside the spreadsheet processor and check whether (price - discount == paymentAmount).

This can handle the whole monthly / yearly thing too. If ((price - discount) * 12 == paymentAmount), then it's probably yearly.