non-linear routing

While setting up routing I notice that a routing is basically a unit of time and that (ending date - starting date) = quantity * routing time

Don't get me wrong, they have their routing set up really badly here (just so NAV won't throw errors I think...) so that may be part of the problem. Keep that in mind if you are graciously taking up my cause.

This linear routing seems unrealistic. For example, we have a customizable machine; it can be programmed to manufacture a wide variety of products. This is a one time cost, regardless of the number of items produced. How is this handled in Navision?