Heres a thought.
Lets say a plumber sets up and establishes a rate of £40 per hour. In his 1st year, he struggles to fill his week, and money gets short, there are rows with the missus, and he wonders if he has done the right thing.
In the second year, his diary starts to fill up, but he has a bit of a mountain to climb, because he ran up some credit card debt paying for groceries in year one, so things still feel pretty tight.
In the third year, although things are much better, the the fear of going quiet still haunts him in the small hours when he can't sleep.
In the fourth year, he toys with putting his rates up, but he loses a couple of quotes, and hears of a bloke in the merchant whose working for £20 an hour, so he sticks where he is.
In the fifth year, things start to get tight for a different reason. He's got plenty of work, but the cost of living keeps on rising, and the missus tastes don't get any cheaper, and anyway, whats the point in being your own boss if you can't go on holiday when you fancy it? Except he can't afford it.
By the end of the sixth year, he suddenly realises that with an average of 4.5% inflation, he shoud be charging £50 per hour. He panics, and shoves the rate up. His regular customers howl at this, so he discounts them back down to £45, gets £50 from new customers, and so ends up averaging £47.50.
Now here's the mental arithmetic test. How much has he lost over the years by not increasing his rate by 4.5% per year?
The answer is a staggering and irrecoverable £55,000. Admittedly taxable, but still a very tidy pile of change, which he can never get back.
And before you tell me that customers are too price sensitive to stand 4.5% per year, answer me this:
Why is it that Aldi and Lidl between them have only 7% of the UK grocery market, and all the discount supermarkets combined have less than 10%, whilst the big 4 "middle priced" supermarkets have 75% market share between them?
Its because the overwhelming majority of people buy based on perception of value, not on price.