I commuted all last winter in Michigan through ice and snow.
I DID buy studded tires at $100 for the pair, but I could have done without them; 90% of the time they were on dry pavement, only hit snow/ice right around storms, most days dry pavement.
I rode the whole winter, including down to -10*F with the following:
1 pair wool socks, 1 pair cotton socks (already had)
1 pair cycling shorts ($20)
1 pair running tights ($15)
1 pair fleece-lined loose running windbreaker pants (had)
1 underarmor clone long sleeve poly shirt from WalMart ($13)
T shirt (had)
windbreaker (had)
fleece scarf (had)
Nashbar 6-in-1 balaclava/neck gaiter/whatever ($10)
Duct tape to seal helmet vents
So my total outlay, aside from the tires, was about $60, and that's because I didn't already have cycling shorts (though having gotten used to them last winter, I bought a couple more pair for summer).
If you're generating the heat I do, this is plenty of clothing. In fact I ran with the jacket 1/2 open most days, unless it was < 10*F.