[AccessD] OT: Pricing Method ?

This is probably a stupid question but.....

When calculating the selling price of an item, say by margin, do you
calculate based on the current received cost, or does one take the average
cost (of previously received items) + the current price and then perform the
calculations?

Total = AverageCost / (1 - m_dMargin)

Or say 

Total = RecievedCost / (1 - m_dMargin)


Another question....

What do you think is the best method of pricing an item in a Service
Oriented business. The business would sell both labor and components..


Thanks
Robert