Buy decent shopping bags then?
And also, the bags for life in tescos, when they break get another and recycle the broken one, if you really want to be tight and buy them. You also get points for using them, not much for me because I don't shop in supermarkets but i'm sure, a weeks shopping, it's about 20 points, better than spending £20.
When i worked in tescos, the amount of plastic bags used in a day was disgusting, you would have a big big big wad of them say 400 bags and it'd be gone within a couple of hours. Most people just chuck them in the bin and considering how much plastic it is, thats a disgrace. Not to mention the amount blowing around in the wind. All because they're too lazy to get some shopping bags, or bring their old ones back in.