Or you could add a date to the CostLookupTable. Of course that would make the table much larger since it would then basically be a history of costs for each item, not just the current. Still, that could be useful information too to retain.

Also, I would change the lookup statement to use an IFERROR and a table name to be a bit more robust. For example, if you name your table CostLU, you do not need to enter the range of cells.

=IFERROR(VLOOKUP(D2,CostLU,2,FALSE),"")