Yes, you're right, it's not. But it's not all about money. I have a friend who is a landscape gardener who set up his business with a partner about a year before I set up my business. They were both making a lot of money when I was still on a very low monthly income. They're still making a lot of money now, though not much more than they used to.
However, since I work on my own, I've never had to put up with the disputes that they have with each other or the other strife which comes along when business partners disagree. (Two heads are not always better than one).
Crucially though, while I've been earning less than they have, my time has been my own. There are not many offline businesses run by a single person where that person can take a month off and still earn $10,000 despite not having done any work that month.
There are three major advantages to running a business based around AM, which offline businesses don't generally have:
1) You don't have to wait for clients in order to work and earn money.
2) You don't have to work sociable hours. You can work whenever you want. If you want to party all night, sleep half of the day and work until halfway through the morning, you can.
3) Most important: you are not geographically bound. You can double or triple your income by going to live in a place where the cost of living is three times as cheap. (If you're from the UK, the weather will probably be better as well).
Being free to work where you want, when you want and for whom you want is rare in the world of running one's own business.