Third creature update.

Hello everyone. In Heroes of Might and Magic V, I created a small mod for the Tribes of the East faction, specifically enhancing the third tier of creatures. However, I encountered a problem. When upgrading from the second tier to the third, it costs only 10% of the original price, resulting in a significantly cheaper upgrade than intended. My question is, where can I find the file containing the script with this 10% (or 0.1) coefficient? Could you please help me locate this file and script, or suggest a way to prevent upgrading from the second tier to the third, and instead allow upgrading from the first to the second, as it was originally designed...?
Thank you in advance. If anything is unclear, I'll clarify.