> Does only committing a "criminal misdemeanor" somehow exempt you from arrest?

It does not - and that's exactly my point! Cops are allowed to arrest that criminal even though there's no immediate need to arrest them. So, immediate need is not a prerequisite to cops arresting someone.

> Right, because arresting people who refuses to show up to court is needed for the justice system to work at all. Otherwise people can just shirk their court dates and never face judgement. There's plenty of other reasons to arrest people besides the two examples I provided, they're not supposed to be exhaustive.

Yes, but cops are also free to arrest people who they are confident will show up to court, if there's probable cause that they've committed a crime. Again, the point of that example was that immediate need is not required before a cop can arrest someone.

> This makes as much sense as calling in the cops to report health code violations.

I agree that it would be best if there were a separate agency that could respond on the spot for this type of issue, other than the regular police department and other than a slow administrative complaint/inspection process which doesn't lead to enough of a fine for stores to change their processes.

But I was discussing the possibility of the sale completing according to the law and the store trying to stop the customer from leaving with their purchase because they didn't pay the illegal overcharge. That would indeed by a crime attempted or committed by the store, assuming the law considers the sale to have been completed, and that is indeed something within the scope of what cops can handle.

To use your health code analogy: sure, in general, administrative complaints are the way to handle health code violations. But what do you call it if a restaurant worker sees something which they know or reasonably should know is toxic to humans spill into a customer's order, and then they serve it to the customer anyway without a warning? Yes, that's a crime as well as a health code violation. There are plenty of cases where cops can legitimately be involved in things that can also be handled administratively. Whether or not cops are likely to respond in useful or timely ways is a completely separate question from what the law allows.

(Tangent: Cops also quite often handle administrative fines of even smaller magnitude than what we're discussing here, but usually when the aggrieved party is the government and the wrongdoer is a random individual, like issuing non-criminal $60-100 fines for not paying a public transit fare of a couple of dollars. It's rare for them to do it when the aggrieved party is a random individual and the wrongdoer is a business.)