You’re the one trying to analyze rape in terms of economics. Presumably you could attach a dollar value for time spent in jail and use that dollar value interchangeably with the time spent in jail (that seems to be an implicit premise of your arguments here). The reason it would be that low is because rape convictions are so rare that you need to discount the cost of getting convicted by about 90% (because only about 10% of perpetrators actually “pay the price” for raping).