My aunt had the same house cleaner for almost 20 years. This person was trustworthy, efficient and didn't charge nearly enough for her services. I think she had a hard time increasing her rates with her long time customers.
When she decided to quit cleaning houses, my aunt had to find a new house cleaner. She was absolutely blown away at what the going rate for house cleaning was.
She had no idea what people were currently charging and getting paid for. I don't think it is always true that you will get better service if you pay someone a higher going rate as each circumstance is different.
If you find someone who charges something less than the going rate, and they give you good service, you would be wise to make sure you continue to use them and let them know how much you appreciate their services.