Can anyone assist me on how to setup Amortization at the item level?

The amortization solution we are seeking is to amortize the cost of a mold over the course of time but we want to bill it integrated into the price of the item on the invoice .   For instance a  $10,000  divided by 500,000 units.   Each unit would carry a .02 upcharge until the $10,000 amount was satisfied.  We want the amortization to end automatically once the $10,000 repayment is complete.    Our thoughts are to utilize advanced pricing and setup an adjustment for customer and item.    However, not sure on how to stop the billing once either the dollar or the