I just checked the official annual budget for all of the penal institutions in Turkey. The 2022 budget is 3.2 Billion Liras[1] ($180M) for about 300.000 inmates in total. Dividing, you get about $600 per inmate per year! (and honestly it doesn't even sound that absurd considering the low cost of living here)
[1]: https://www.sbb.gov.tr/wp-content/uploads/2021/10/2022_Yili_...