Speaking of Costco, the Head gloves they sell at this time of year are one of the greatest deals in ski accessories. They are waterproof/breathable, have Outlast for temperature regulation and also have a zipper slot on the back to insert a heat pack if needed. All of this for $16.99. Last year when I needed new gloves I bought 3 pair.
For warmth I'm also a big believer in glove liners, especially important when you need to take your hand out of your glove to retrieve something from a pocket, etc. Glove liners plus the Head gloves will take me comfortably down to zero F or so. Colder that I use mittens plus glove liners. I have not needed to use heat packs in gloves, though I rarely have to ski in the temps that some of the easterners and Canadians do. I have needed to use the adhesive heat packs on the toes of my boot liners a few times though.
Season length: 21 months, Nov. 29, 2010 - July 2, 2012
Days in one year: 80 from Nov. 29, 2010 - Nov. 17, 2011
Season vertical: 1,318K in 2010-11
Season powder: 291K in 2011-12