The price shown depends on whether the product has been associated with a supplier and whether there is a pricing rule which applies to it.
The rule is:
if the product IS NOT associated to a supplier then, the default purchase price is fetched. The pricing calculator stops and and the default purchase price is returned in the order.
if the product IS associated to the supplier of the purchase order AND the supplier price is greater than zero then, the selected supplier price is fetched. The pricing calculator stops and and the selected supplier price is returned in the order.
if there is a purchasing pricing rule that applies, then, the purchasing rule is used to calculate the purchase price to use.
A similar reasoning applies to selling and client prices.
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