what default unit cost shows up when you create a new PO manually for the item from the preferred vendor?  check the vendor pricing files.

For some reason it shows as a crazy price but when i check item maintenance and vendor maintenance that crazy price doesn't appear . See pic below

Here are 2 KB articles. I believe the hierarchy may answer your question. What is the Item Cost Hierarchy_.pdfWhen a Standard PO is created from a Master_Repeating PO.pdf