The part number for the hydraulic valve lifters in my car (and in many of our cars) is 17122490. I can get them for around $30 each.

I found information that says GM part number 12499225 is a package of 16 pieces of part number 17122490. The price on GMPartsDirect for 12499225 is $109. You get 16 lifters for a little more than the price of 3 if purchased individually.

I sent an email in to GMPartsDirect to confirm this, and will let you know how they respond. If this is true, it would be good information for our members.