Yes. your understanding is right.
Item Price is taken from 'list price' field in 'Purchasing' tab of Item master (Org level)
The items that appears in iprocurement can be also from BPA(negotiations), in that case it can be from BPA line price. Also Price will be having an effect if any price break exists in the agreement.
Item set up Org level -Purchasing Tab-List Price
Item set up org level-Tools-Categories