The last time I hit Joanns for the batting sale I too figured it out by the yard and the prepackaged worked out to be a little under $5 per yard for queen size which is usually 90" x 108". 108/36 = 3 yards. The sale price about 3 months ago was I think $13.99 so it worked out to be only $4.66 per yard.
Using currently published on line prices which may not be right... A full 40 yard roll of 90" W&N is currently priced at $315.60 that works out to be $7.89 per yard. Prepack queen size warm and white batt is priced at $15.59 which works out to be $5.19 per yard. I noticed that on line warm and white costs a tad more then the regular beige colored W&N