I’m totally in favor of mild punishments and I do think that imprisonment is barbaric and should be avoided if at all possible, but money as a punishment, for example, is not without problems.

It basically gets rich people of the hook. If there is a flat rate to pay, that’s the case anyway, but even if the punishment is a percentage of someone’s income, this disproportionally hits poor people. Poor people need all their money to survive – pay rent, pay heating, pay food – there is nothing extra, no money to save. Once you are making several dozen times that money, a monetary punishment hits you disproportionally milder.

It’s funny that you seem to be worried about the poor for which this type of punishment is probably absolutely devastating and not very likely to have any positive results at all. The poor are a problem, not because they might not pay, but because the punishment might be excessive and not lead to a positive outcome for them (i.e. it doesn’t prevent repeat offenses).

Preventing repeat offenses and being a deterrent seem like the only two legitimate justifications for punishment to me, and I’m not sure whether money can do that.