PO detail lines missing cost fields

Hi, using 9.2.  We are testing some POs with new EDI suppliers and I stumbled onto something that is odd.

In the attached export of F4311 for test POs entered today, a user DBELLMANN entered two two-line purchase orders 2238683 and 2238684. 

In each of his PO's one line has the Purchasing Unit Cost (AMC3) and the Extended Cost (ECST) populated; but the other line doesn't.  You can see that other users' PO's have the fields populated. 

I've read the help but cannot tell how these fields get populated....why would one of his lines have it and the other not?

He is a new user to entering PO's and I'd like to give him some feedback...