I bought mine off of ebay
. This is the seller I bought from: tackmarket
The blankets were cheap. I think they were like $50-60 a piece including shipping. I just ordered the cheapest ones I could find because I live in a normally mild climate and we got a freak snow storm for the first time since the 80's and the seller was only 2 hours away, so I knew shipping would be fast. I didn't care too much if the blankets lasted as long as they got me through the week. They held up really well though. I think they'll last at least another 3-4 years, if not longer.
One warning, though: I'm not sure if I'm just not good at measuring (this was my first time buying blankets), but it seemed like the blankets ran a little small, so if you order from them be sure to order at least a size or 2 too big).
If you want it to last, make sure you get the 1200 or 1800 denier or whatever the highest number you can find is. The higher the number, the tougher and more water resistant the blanket is.