I run a small cleaning business that brings me in some passive income, but when i was at the start i had this client that i eventually refused to do work for be

I run a small cleaning business that brings me in some passive income, but when i was at the start i had this client that i eventually refused to do work for because he wasn't worth the hassle. The bill for a months cleaning of his office was £500-ish. The guy was part of a family that owned an Oil and Gas equipment company that must turn over hundreds of millions of pounds per year, and that guy REALLY REALLY didnt want to pay his £500 bill for an office clean. He must have spent about 10+ hours going back and forth through emails and phone calls querying 2-3 hours here, the cost of cleaning supplies, complaints about the cleaners i'd sent, just to get his bill down, in the end his bill was down to around £400 and he eventually paid it, but he'd wasted his own time and the same amount of my time. Now i consider 10+ hours of MY time to be worth WAY more than £500 due to what i can earn doing my usual consulting and also because i dont want to deal with douchebags like him, and what i make per year is insignificant compared to the company that he helps to run, so i never understood why the hell he's kicking up shit over a damned cleaning bill. Infuriated me to no end. Now i only have clients that pay their automatically issued invoices every month without issue, they're happy and i'm happy, i get my beer money and i can concentrate on my consulting instead of my side business.