cover it up!

This fall/winter season, Prince Charming and I would like to cover up our main room windows with something that will also assist in keeping the heating bill lower than usual. Over the course of the last two hours, I have now gotten my heart set on these...

gorgeous gray wool curtains
from West Elm

...however, these curtains cost roughly $100 per panel and we need six of them! Do you know of any more affordable options? [Our windows span 135" wide and over 100" tall.. and we have two sets of those.]