Variations price adjust based on previous variation Using Drupal Commerce, is there a way to adjust the variation price base on the first or second variation selected?

For example I have 3 variations: size, material, color. If I choose Small (that costs $5) and material that costs $10 ($15 total), then when I choose Large at $12, the material should cost $20.

I guess I should use rules. Has anyone done this?
http://www.drupalcommerce.org/user-guide/product-attributes-variations - here you can read about product variations, don't forget to enable field as an attribute field that can change the Add to Cart form

After that you need to create products for all variations with right prices. You can use http://drupal.org/project/commerce_bpc