In general, restaurants operate on very small profit margins. That's a fact that many people need to understand. Their menu prices are not intended to gouge your wallet but rather to support the functioning of the restaurant, to pay the bills, to pay their employees, and to hopefully give at least a small profit to the owner. Those are the same basic objectives of any for-profit business.
Some people seem to believe that if they can find a food item for a cheap price somewhere, that the same item should be priced similarly everywhere. However, just because you might be able to get a cheeseburger for $1.00 at a large chain restaurant doesn't mean all restaurants should charge that price. There are numerous factors to consider in evaluating the price of a burger and whether it's reasonable or not.
The same applies to the famed Vietnamese sandwich, the Bánh Mì. Some local Vietnamese restaurants have offered very inexpensive Bánh Mì, from $4-$5, and that has led some to believe that Bánh Mì, at any restaurant, shouldn't cost much more than that, and especially not over $10.
I know two newer, suburban Vietnamese restaurants which charge $11-$12 for their Bánh Mì. I consider both to be reasonably priced and I don't see any reason to complain about the prices. Both places have received some feedback from others that their prices are too high, and I've also personally heard from a few people complaining about their prices. These complainers are failing to properly take into consideration all the factors going into pricing.
For example, what is the cost of their ingredients? If they are using higher quality ingredients, then their costs are higher so they have to raise their prices. Would you rather that they used cheaper, lesser quality ones? Are they using just any baguette, or do they have a bakery especially making baguettes for them? How much work goes into the preparation of their Bánh Mì? Are they slow cooking their meats, marinating them over the course of a day or so? Are they making their own pickled vegetables? Are they using house-made sauces?
Consider as well that these Vietnamese restaurants are generally small businesses, not some large chains. They need to price their items appropriately so that their business can survive. In addition, they are often run by passionate people who want to serve their communities, to share their love for their native cuisine. Their goal is not to become wealthy but rather to make enough to live. If you speak to these owners, you won't get the impression they are trying to gouge or overcharge their customers. They are trying to fairly price their items.
Consumers need to start paying the true value of the food they consume. They shouldn't expect that certain types of food must always be cheap. They should think about their own business, and whether they would be happy charging the lowest price in the market for their services or products. Stop complaining about Bánh Mì prices and simply enjoy that delicious sandwich.