Customizable Products with Shared SKU's

Taken from post in drupal commerce.
http://www.drupalcommerce.org/node/384

Anyway, I'm working for a manufacturing company that sells customizable products, wherein about 100 base SKUs can have many attributes applied to them. Line Items (just a new nomenclature?) make sense (at least in the Manufacturing world) here, but enforcing that every combination yield a new product does not.
Have I misunderstood the Commerce initiative? As of yet, Ubercart is an easier to understand solution, but I like the flexibility available to me through Drupal Commerce.

Take, for instance, a car. The auto manufacturer might sell model X-123 with over 50 various attributes applied to it. But not every combination of those attributes changes the base SKU.

Nowhere on the demo site, on Drupal.org, or here, have I found anything that clearly describes what a "Product" is, what a "Line Item" is, and how they are properly associated with one another--to the visitor, the store manager, or the site administrator