Surely it depends on the income level? There are people for which a $20 USD lunch everyday or close, is nothing to write home about.

In fact their time can be far more valuable (into what money they can command by doing some extra work), so that the opportunity cost between cooking and buying lunch to make it not worth to cook.

I'm just pointing out that the demand for eating out is highly elastic. If the restaurant industry as a whole raises prices relative to background inflation, then overall sales will fall and some will go out of business.

The probability of the food from a restaurant being sufficiently tasty/nutritious is way too low compared to the effort required to make it at home for it to be worth spending 20GBP eating out all the time.

I also simply choose to eat out a maximum of 1 or 2 times a month. I can afford 20GBP, I just have better options.

That's pretty much the prices in Norway. To be fair Norwegians do eat out less than in other places as a result of it.

That’s about 15 minutes of labour for a software developer. So less time than you’d spend eating it.