Calculate a cost based on PickLists

Hello,

I'm trying to build a formula based on 2 Pick-List fields, the first one with 8 values, the second one with 4. Each combination of these 2 fields corresponds to a cost (known). So, there are 32 combinations to achieve.

I tried to use nested If statements, but I get an error message "The formula entered is not optimized for performance or is too complex. Please optimize/simplify the formula and try again."

From my tests, I found that there is a limitation of 21 "If" statements in the formula.

Do you have an idea to achieve my formula?