Put your part number into the main search entry field. It'll give you the price.
Click on CATALOG, find your part number, go back to the main page, and put that number in the search field.
1990 Bonneville O2 from GMPD:
GM PART # 25162693
CATEGORY: Computer Control Sensors
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $56.92
OUR PRICE: $29.60
Dealer retail is the higher number. GMPD price is the lower. Add shipping. If you order multiple parts, you'll save on shipping.