I don't buy McDonal's because the price/value equation is off. Whether it is off because they think I'm rich or because they think I'm addicted doesn't really matter. The result is that I just don't buy.
But if I was a regular customer, I would see unstable prices as a negative because it means, I have to research current prices first before going there. That's inconvenient. I prefer reasonable and stable prices.
Maybe, McDonald's introduces haggling next so customers can feel like they are buying a used car when they buy a burger...