Item Price Problem for BOM

Even if the product price during BOM creation. (Last Purchase Rate not found for item BLABLABLA) error. However, I did not buy the product I will use the BOM. I just got an offer from the supplier. Because if the person I bid on accepts my price, I will make a purchase. I do not want to enter that price manual.

Sorry for my english I use google translate. I hope I understand what I wrote.