Hehe.. someone in the mac_cosmetics community pointed out that MONISTAT Soothing Care Chafing Relief Powder-Gel is very popular on Makeupalley.com as a FACE PRIMER and I searched the MUA boards for it.

MONISTAT Soothing Care Chafing Relief Powder-Gel:
A revolutionary friction-fighting Powder-Gel™ formula that creates a silky, breathable barrier on sensitive skin to prevent and relieve chafing and irritation. It also works to soothe skin post waxing or shaving.

Apparently it has the same ingredients as the Smashbox primer and works just as good as Smashbox for only a few bucks.