Now through the end of the year, the Honeysuckle Breastmilk Storage Bags, 300 count are on sale here for only $39.95 with free shipping. That makes each bag only .13 cents each! They normally retail for $72.95. This is a steal.
Other package sizes and oz amounts are on sale too, but this one is the best bang for your buck.
I personally use these and have not had any issues.