You can include inequalities in a relationship and thus set up a lookup process that looks up values based on a range of values instead of just a specific value or you can define several pricing fields with the break quantities and define a calculation field that selects the appropriate unit price for computing the line item cost.
Using the second option:
Your Price table for a left handed widget might look like this:
ItemID Description UnitPrice1 Break1 UnitPrice2 Break 2 UnitPrice3
123 Left H Widget 3.50 50 3.00 100 2.85
Your Line Items table would have the same fields set to use looked up value options to copy all these data. Then, your item cost calculation would look like this:
Qty * Case ( Qty < Break1 ; UnitPrice1 ; Qty < Break2 ; UnitPrice2 ; UnitPrice3 )
Thanks for the input. I wasn't sure how to tackle this.
Once I get a chance I think I will implement option 2.
Thanks again for the quick response.