title: Looking for patterns/best practices for calculating complex discounts
body: <p>I'm developing a price calculation engine. I've looked all over and there's nothing that really fits what we need. However, I'm now looking how to implement specific prices and/or discounts. I don't want to introduce a rule based engine to my end-users, because they won't get it.</p>
  
  <p>For example, when you order an ItemX the price is $30. But in combination with ItemY the price of ItemX is $20. Or when ordering five of ItemX, each after it will be only $15.</p>
  
  <p>Any ideas on where to start? How to take this on? Perhaps some (open source) example applications that contain practices like these? Any (technical) patterns I could use? Preferably in C#.
  Thanks in advance!</p>