Is it possible to use "Discount" achieving your result?
Example:
1. Go to shop/Discount and make a group 'G1".
2. Go to group "G1" and add a rule "rule1" which might specify having 12% discount of product X to these discount group. 3. Adding user groups to these discount group.
Then if the price for other groups is 100 kr, the discount group will get 88 kr.
we had a similar problem. discount-groups doesn´t fit the needs of our customer, because the prices are not calculatet by discount rules. the basket-module of ez also takes the first element of the class, which has the datatype "Price" and takes that price out of the product-object.
we implemented an extension. the extension provides some "basket" functions like adding one or more articles to the basket. we "copied" the basket-module to the extension and added some more functions.