So, ...
| A | B | C | D |
-------------------------
1 |price| ID | ID |price|
This is the situation you got?
In column E, put
VLOOKUP(B1; C:D; 2; FALSE)
Depending on your regional settings, the ;
might be replaced with a ,
This will give you the price in column D when the value in column B can be found in column C
If it cannot be found, you get an #N/A
error