You made a good point and I immediately thought that reporting a gross profit dollar amount as an example of how profit margins are not slim as simply inappropriate. And I would have responded myself if you hadn’t. There’s no single dollar figure that can inform anyone about anything useful about the profit margin of a business. A number without context is useless.
New Jersey has a law like that for gas. Can only increase the price one time per day. But ut doesn’t apply to all gass stations, just ones on the highway rest areas.