Just FYI, I did just get recent prices from my dealership about their winter packages.
They offer the Michellin Pilot Alpin PA3's on Double Spoke 270M rims with the TPMS for 1865 euro (excluding VAT if you have the form). Estimated about $2.4k with today's exchange rate. A little too pricey for me... Plus, I won't be driving it much during winter, since my other car has winter tires and I will be shipping my BMW back to the states early so it can meet me there.
In all honesty, I think a set from Tirerack is the way to go, unless you are looking for something very specific or OEM. I may be going OEM if I can find the rims and save the money, but it probably won't be until next winter. If I do go with a winter set, it will probably be from Tirerack so I can save some cash