Most people have the minhag from before the war. It’s not a chumra that I’ve seen individuals take upon themselves. I’m sure there are some, but it’s a small minority. So, they are not allowed to change, in most cases.
Besides, your assertion that it affects anyone else is baseless. You even reported that you found the cheaper gebrokts cookies in your store! The companies which I’ve seen make them, Streit’s and Manischewitz, make them in huge quantities, so the price isn’t affected upwards by the competition.
Mw13 ably demonstrated that your logic (which is wrong anyhow) could precisely be used to show that there should only be non-gebrokts sold, which again, you never rebutted.