I did some back of the envelope math on these a few years ago based on Amazon's truck numbers and proposed profit figures and they were between $7.18 to $28.74 per day per driver. This was based on Amazon's optimistic figures.

With Amazon putting those numbers in the proposal, the real numbers would almost certainly be worse. Between minimum wage and gas, that margin is eliminated.

These are the urban equivalent of the contract chicken growers. Give them a flat rate and make them absorb increasing costs.