How many balls of yarn do you purchase of the same colour and type at once?

I've started listing yarns 'by the bag'

View Steals and Deals by crochetgal on Etsy
at what is now approx 50% off the regular retail price.

There isn't any limit to the number that can be purchased at a time and I do offer a layaway for those who don't want to blow their entire weekly grocery budget on yarns. (you can spread the payments out over a few weeks)