calculating cost prices for a product with multiple variables

Would appreciate some help with the following problem.

I am putting together a formula that will calculate the cost of a software sale.

There are two variables of the sale, the number of users (USER), and then the level of support (SUPP) required for the software.

The cost of sale for each of the variables of the sale is based on a discount to RRP.
The discount to RRP varies by product and also varies between the two variables, eg.a different discount for software users (say 50%) and software support (say 25%).

USER = a non linear relationship of between selling price and number of users, eg. 1 user = 100, 2 user = 190, 3 user = 270 etc.
SUPP = choice of three levels of support (eg.bronze, silver, gold) and also a non linear relationship between users and selling price, eg.1 user bronze = 25, 2 user bronze = 40, 1 user silver = 50, 2 user silver = 80.

I'm trying to produce a formula which will enable me to input into three fields eg. product, number of users, and level of support - and out will pop a cost price for that sale.

Each product also has a different max number of users.

My current attempts at the formula are cumbersome and will be difficult to maintain when sales price lists are producted.

Would much appreciate your input, thanks