It used to be 10$ when it was introduced at the end of 2023 up until 1.6.10 (which released in November 2024) when it changed to 15$ because we felt it to be more fair to our patreon supporters who paid a lot more monthly to have updates to the game.
It stayed 15$ until November 2025 when, since we didn't want to be shadowbanned, we were forced by itch to remove all forms of payment due to the game containing adult material.