I'm not into Google Sheets, but if the Vlookup is the same as Excel, you need to tell it one more thing.

=VLOOKUP(A4,Sheet2!$A4:$B13,2, FALSE)

The reason is the default is to have an approximate match. If the price codes aren't sorted, or if you try for a code that doesn't exist, then you might get a false answer. In this case, you need an exact match, which is what FALSE forces.