Personally I just came back to wow recently and had 1 85 lvl team and a bunch of 60s so I decided to go the route of keeping my main account and doing RAF on 4 new ones. I had already bought my 4 battle chests prior to tuesday so i paid $19 but if I understand correctly if you buy vanilla you get BC for free and when I last looked vanilla was selling for less than $10 in a few places.

Looking for a deal on WotLK now.