u can consider tollyjoy breastmilk bottles from many dept stores. it's selling at $9.90 for 4 bottles and with GSS recently I just bought from metro with 20% discount at $8. so it's $2 a bott for brand new bottles.
bottles are more economical cos in the long run it is cheaper than the bags. However, milk bags save the trouble of sterilising ans is good to store long term in the freezer. I m also using autumnz milk bags to freeze in freezer or whenever I run out of bottles. I have 20 bottles but somehow I do run out of bottles once in a while when my baby doesn't drink much for the day.