1. First, prepare the sample table.
2. In any cell create a drop-down list to choose the products from sample data you've just created. Use data validation for that.
3. Click on the cell right to the drop-down list.
4. Write the formula =VLOOKUP (value you are looking for, table array, column number, false)
4. If you can't write that formula just copy/paste mine: =VLOOKUP(E3;B3:C10;2;0)
5. Your spreadsheet is ready:
Here you can download this spreadsheet for free.