Incidentally “paying your debt to society” and “serving time” are entirely misguided concepts with no relevance to today’s prisons, which are about control, power, and violence. /Good/ prisons would be about forced rehabilitation and fixing the problems that led to the crime, or else simply keeping the hopeless cases locked up where they can’t cause trouble.

Not only treating time as a commodity with a price, but “money” itself is a very new, strange, and abstract thing in the history of human culture. For most of the time homo sapiens have been on this planet, they’ve done barely any trading, most of that was with relatives, and they had no concept of money. Same for “investing,” or the general concept of a “commodity.” Personally I’m gung-ho in favor of all these abstractions, and of pushing them farther and creating new ones, such as “information” in units of bits or “bandwidth”, an even slipperier concept that deals with things like lag, reliability, and privacy, as well as bits per second.