Problem:

Retrieving the matching price of the item shown in cell A2, for the specific brand entered in cell B2.

Following are the prices for each possible combination:
Item,Brand,Price
Jeans, Diesel, $85
Jeans, Levis, $80
Jeans, Lee, $70
T-Shirt, Sacks, $7
T-Shirt, Gap, $5
T-Shirt, Old Navy, $3

Solution:

Use the IF and LOOKUP functions as shown in the following formula:
=IF(A2=\"Jeans\",LOOKUP(B2,{\"Diesel\",\"Lee\",\"Levis\";85,70,80}),IF(A2=\"T-Shirt\",LOOKUP(B2,{\"Gap\",\"Old Navy\",\"Sacks\"},{5,3,7})))