Maybe the manufacturers have figured out that we are on to their evil scheme of telling us to replace them every month. So they are making them cheaper to force us to replace them sooner?
I have not bought bio bags in a long time. I just used the frames inside the biobags and recovered them with the white/blue cut-your-own material from my LFS
. I just did a fast whip stitch with fishing line around the edges to hold two pieces in place, like sewing two pieces of bread to a piece of cheese.