Yeah but ridiculously high prison sentences don't make sense still from the standpoint of why we even have prison sentences instead of say a death penalty.
The one reason you have a prison sentence over a death penalty is not that they have an equal amount of punishment to do with community expectation; after all then we would not only have death sentences, but also have to allow torture as a way of a 'disincentive' to criminality.
No the reason you have a sentence and not straight state ordered murder, is you believe that people can be rehabilitated and allowing them to 'prove' that they are on the right track and thus have a sentence reduced is an effective balance to the idea of some form of impactful & meaningful penalty to the individual so that they can learn (note not set an example).
What you are saying effectively with a ridiculously huge sentence is we sentence you against the spirit of our judicial system (to rehabilitate) to an agonizingly slow boring death in jail; and that you may as well not try to rehabilitate yourself and as such become more vicious and 'evil' because there's no incentive for you to become better.
In what way then do you decrease criminality in any way more than a death sentence and yet; I don't know how they do prisons in turkey, but in Australia that's a whole lot of extra punishment going to taxpayers who did nothing wrong who could use for example a more effective & responsive police force for what are arguably worse crimes then effectively destroying some investment funding.
You know rape, murder and kidnapping.