Those with qualifications or experience get quite well paid. The average salary of an employed plasterer, for example, is £13.75 per hour hereabouts or £27,500 per year. That's pretty good. And that's the average salary; a skilled plasterer will earn more and the person running a company of plasterers much more. One of my neighbours was the last - he employed plasterers and other trades, about 100 people in all IIRC - and was worth a mint. No, £13.75 per hour is not megabucks, but it's well above minimum wage and it's a gateway to much more. An acquaintance has a business selling slightly specialist pipes, valves, pipe fittings, and the like - humble stuff, really - and drives a Bentley, which was new when he bought it.
You should read the start of 'The Millionaire Next Door' - you wouldn't notice most millionaires.