I totally support the idea of not giving away free plastic bags during shopping. I am also fully aware of the Earthly situation we are facing this century, as I have written an article 18 months back.
The only problem though, is: how many people bring out empty plastic bags?
I tried. I really tried. Some time back, Cold Storage encourages recycling of used plastic bags. So I did put some plastic bags in my document bag and whenever I buy groceries after work, I would use these bags.
But many times we do unplanned purchases say during lunchtime, when you typically don't bring any bags except your cash. Then I end up getting more plastic bags. And frankly the idea of buying durable shopping bags do not help much, because people will forget to bring these bags out, so they probably end up using the issued plastic bags.
Some stores like IKEA and NTUC Fairprice works because you can trolley your purchases to your car park and transfer the load to your car, so they can afford not to use plastic bags.
But charging for plastic bags is not the point: the point is conservation. With our affluent society, people might not mind paying 10 cents for the bags, so it defeats the purpose. Sometimes, we really do need these bags. Look at the families buying groceries en masse for hundreds of dollars, filling up no less than 10 plastic bags. You wouldn't expect them to buy the costly shopping bags: if each were to cost $2, then they would have to pay $20 for the carriers.
I have a proposal. Customers pay for the durable shopping bags in the full value (say $2), but they can also return the bags to get a full refund. This way, customers will be encouraged to bring the bags back to the store to get back their money, and meanwhile they could do some more shopping and use the bags anyway.