Is banning them really the solution? People need to be able to carry their stuff. If plastic bags are the best option, thats just the physical reality of the situation. Arbitrarily banning things left and right isn't going to fix that.
GP was talking about banning paper bags I believe
The current market price of plastic bags doesn't reflect the externalities of using them willy-nilly and throwing them out.
Increasing the cost to well above pocket change might have the welcome side effect of making people care more, but IMO that's a secondary concern.
We use sturdy hemp bags for our groceries. They cost $1.50 or something like that and last for years. And it's hemp, so it should degrade like other natural fibers.