I look at it this way.... I make as much money as I WANT.
There are guys out there (granted I am in Oz) who are "flat out" doing ten jobs for $300 each. That's $3000, the same $3000 that I charge $750 for each of 4 jobs. I take my time, do a better job, have pride in my work and have no stress and always deliver on time. I don't have another 6 people asking where their job is. Fixed costs - rent, utilities, lights etc are going to be the same whether you do 10 or 2 jobs, whether you are open 1 or 24 hrs per day.
I have NEVER given two hoots as to how much someone "turns over" as in gross. It's what's left that counts. In some years, I have made more money than those turning over millions of dollars.
Busy does not always equate to profit. Consider how the guy that spends $25 on a litre or quart of paint can turn that one can into $10,000 just because of what he can do with it - splash it on a wall.
How much money can you make in this business? Too many variables, such as materials, individual supplier costs for same product availability, outgoings, staff, stuffups, fuel costs, general business confidence, who your competitors are - their pricing: who they know: how good they are: how ambitious they are, even down to the weather and how this affects dry times, installs, courier deliveries for stock, staff illness etc etc etc.
If you are a good business person, you can make enough money to do the things in life that you want to do. If you are passionate about doing something that you absolutely love, then it is a joy to go to work each and every day.... and get remunerated for it.
Hope this gets the cogs ticking... my point really is do what you love and you will be happy. THAT'S what life is about. Lotta dead rich people.
Cheers - G