Why not offer both? In a manner similar to AWS, let me have the option to pay for a fixed amount at a slightly lower cost and pay for additional "as I go" at a

Why not offer both? In a manner similar to AWS, let me have the option to pay for a fixed amount at a slightly lower cost and pay for additional "as I go" at a slightly higher cost? If I have no way to predict my baseline usage, I'll just stick to using the no-guarantee price. But once I have an understanding of a baseline usage amount, I'll commit to paying you in advance for a certain amount in exchange for a slightly lower rate. If I don't meet my goal/quota, I lose it. If I go over, I can buy more at the variable price. Why does it have to be either/or?