How to get costprice when creating SalesQuotationLine with AXSalesQuotaionLine class?

Hi. Everyone:

When I create SalesQuotationLine with AXSalesQuotaionLine class,

How can I get item's costprice ?

I found out if I didn't assign it manually. it would be 0.

However If I create line in SalesQuotationLine form, It will has value.

I try to to set a breakpoint in insert() of SalesQuotationLine. It stop there and already get the value., However I cannot find where the value comes from.

Can Anyone shed some light for this? It would be appreciated.!

Quatrani