Link with Video - (Watch in full screen for better resolution).
As you can see, when I add an existing product to the Opportunity, I have a 2013 price list selected. When in the product page - I choose 'Use Default' pricing and set a quantity.
On load - no price shows up - nor extended amount.
I verified to check that the Product was included on the 2013 price list as well as verified the pricing.
Potentially significant (New price list items were uploaded recently to the system, however we have not had this issue before).