Automatic product variations pricing
How about the Commerce Customizable Products Module.  I just saw this video today, maybe it will help.

Drupal Commerce allows you to sell customizable products that require customer input when added to the cart. Use cases for this functionality include:

Business cards that require contact information and a logo upload.
Event registrations that require attendee information.
Donations the allow the customer to specify a donation amount.

The core Line Item module accommodates these scenarios by letting you add any number of fields to the Product line item type and expose them to the Add to Cart form. However, sites that sell multiple types of customizable products or a mixture of customizable and non-customizable products need to define multiple line item types to handle the different configurations of fields. That's where this Customizable Products module comes in!
It gives you the ability to define new line item types on the fly at Administration &gt; Store &gt; Configuration &gt; Line item types. This is functionally equivalent to defining the new line item type in code, which is still recommended if you are able.