No. Scaling jail sentences based on income would mean that the monetary size of the punishment was (roughly) constant between a rich and poor offender; just lik

No. Scaling jail sentences based on income would mean that the monetary size of the punishment was (roughly) constant between a rich and poor offender; just like if they were charged the same number of dollars as a fine. However, just as with fines, it would mean that the subjective effect of the punishment is much greater for the poorer person. If the goal is deterrence, then we need care about how subjectively costly the punishment will be to each person. Having a high income doesn't make your time subjectively more valuable, but it does mean that you can trade it for more money. A rich and a poor person would likely value a day of their own time quite similarly, but they would each value $100 quite differently.