All of the examination of costs in the comments assume a zero cost of enforcement. Free courts, free police, free jailing or fine enforcement of any violators.
Without that free enforcement, these $5-$50 items would not be worth fighting over.
I don't believe that police protection should be a fee-for-service business, but are there no checks and balances on the use of public services for private gain?
Your argument applies to theft of any low value item. If a shopkeeper presses charges against a shoplifter, are they using public services for private gain? Should there be checks in place to stop shopkeepers from reporting too many thieves?
It would seem from the article that the business model not only requires the free protection, but that the enforcement of fines an judgements is a major driver of revenues.
In your hypothetical example, I believe you are referring to a physical storefront where the primary revenue generating activity is to sell merchandise.
If your hypothetical shopkeeper had a shop that made more money from forcing shoplifters to pay a fine for scaling, then... perhaps. I don't think your hypothetical shop exists, so it's tough for me to answer.
Without that free enforcement, these $5-$50 items would not be worth fighting over.
I don't believe that police protection should be a fee-for-service business, but are there no checks and balances on the use of public services for private gain?