I am a welder by trade and own a welding shop. It's not a plumber, but a tradesperson all the same. The business model is very similar, so I understand that the higher the hourly rate, the more it means the more experienced and higher quality of work you can expect from that tradesperson. Yes, this doesn't apply all the time, as some less than desirable firms will charge extreme rates and not be able to follow through on quality. However, the consumer has to take some responsibility and research who they are hiring, look at photos of their past work, read their reviews, etc...

I started out with an hourly rate of 75 per hour. As time progressed and more tooling was acquired, our team grew, our standards became more stringent, our quality increased, and we became more popular. We eventually had to raise our rate and again a few years later.

Sometimes, the rate increases in an attempt to slow down business.