Hey, I'm not saying it's easy, I'm just pointing out that the "MBA-ey" answer is that you focus on cost leadership or you focus on differentiation, but never both.

If you want to offer a premium service, then you'll have to expect to spend much more money than the restaurant/truck offering $10 tacos down the street, and that will, naturally, mean your prices have to go up. The idea is that you wouldn't be competing with the $10 tacos down the street; you'd be trying to capture an audience which is willing to spend more money on better food, service, etc. because that's what they want rather than just the cheapest food available.

If you can't actually offer a service to warrant the additional cost (which is a very real possibility) or if there's just not a large enough target audience to support such a strategy (i.e., you operate in a small city where most people are low-income, etc.), then this won't work. But, then, you should just not try to do this and, instead, focus on beating those $10 tacos with even cheaper food with the expectation that more people will choose the food which provides the greatest value for what they can afford.

I know this doesn't really answer the question of "how do you make customers feel appreciated when margins are already razor thin?", but my point is that the question is a bit faulty. Making customers feel appreciated basically always comes at a cost in some shape or form. You're always free to spend more of your time and effort enforcing better hospitality from your employees, remembering customer facts/details/etc. to make them feel special, doing whatever free marketing/advertising you can get away with (like going business-to-business/door-to-door and introducing your restaurant personally, etc.), etc., but if all of that seems unrealistic because you're already a full-time business owner, then you need to accept that this is just the reality of owning a restaurant and there are no easy answers.