I apologize if I have titled this question incorrectly.
I am selling products online. Customers can purchase the products plain, or they can purchase it with one of two logo design applications, printed or embroidered.
I intended customers to benefit from bulk quantity discounts increasing as they purchased more products.
I initially intended to offer the following discounts
Product Price 4% 9% 15% 22% 30%
Embroidery 16% 25% 33% 50% 58%
Printing 8% 16% 25% 41% 58%
The quantity bands to which discounts are applied are consistent throughout all three categories. The quantity bands are as follows:
1-4 items (no discount)
5-9 items
10-24 items
25-49 items
50-99 items
100+ items
Product prices range from £2-£200.
The base prices for both Embroidery and Printing are fixed at £5.99.
For example lets say someone wants to order 17 of a product that has a unit price of £19.99 with embroidery customisations.
The following two rules should apply:
Products
17 x £19.99 = £339.83
15% = 50.98
£339.83 - 50.98 = £288.85
Customisations
£3.90 x 17 = £66.30
Total
£355.25
For technical reasons I can only incorporate one discount rule per order. Therefore if a person wants to order uncustomised products I am able to apply the discount rule. However, if they order customised products I can only apply a rule that now needs to incorporate both the product discount and customisation discount.
How can I calculate the new rule for customisations that will correctly incorporate the desired combined discount in one rule?