All Mark has to do is reduce his price a little.
People will then rationalise their decision to buy Mark's honey by telling themselves that if the price was the same they'd buy Barry's because they care about the bees.
Exactly! Then they start a race to the bottom, take up debt, and spend on marketing until one goes bust! By then everyone is buying imported synthetic honey which is way cheaper anyway. Heil capitalism.
They get a product which is worse, but in very non-obvious ways, and has some sort of negative environmental impact that is hard to identify until years later.
The biggest problem with modern capitalism is that you don't know if something is "good" before you buy it. The information asymmetry / obfuscation ensures that.