Think it though. If you could make more money long term while using cheaper ingredients or similar cost saving measure then what's to stop you from doing that without the tax increase?
Depending on the circumstances, that's a big "if". If your not-so-cheap ingredients are one of your restaurant's selling points (even if not explicitly), using cheaper ingredients could reduce your sales such that the savings turns out to be a wash, or a waste.
I think this happens all the time: it's not uncommon to see a restaurant review that goes something like, "I'd been coming here for years, but the quality of food has gone down recently". Granted, you don't know why: maybe they switched to cheaper ingredients, or maybe they got some new cooks that prepare things poorly (or even just differently), etc. But some type of cost-cutting measure could be to blame. And if that person -- and others (and perhaps potential new customers who see the recent bad reviews) -- stops visiting or visits less frequently, those cost-cutting measures may turn out to not have been worth it.