I don't really want to compare my playing with wood to the great work I see from some of the knife makers here, but I have been thinking about that question myself recently. I had started making knife handles to do something creative and productive that gets me away from the computer and shows results faster than the work projects I am usually involved in. The fact that some people liked what I made was not only an encouragement, but selling pieces allowed me to buy better tools and better wood, so work became even more fun. I am terrible with money and worse with book keeping, but according to my tax files even after selling quite a few of my handles, I still have not made much money overall because I just spend whatever I made on more wood and tools. So, money is really not the driving force here.
What made me think about the topic recently were the changes after renting shop space. While it is an incredible relief to not have to work in my living room anymore and to have all my tools set up in a dedicated space, I also now pay rent that would get you a nice apartment in other parts of the country. So now I have to 'produce' in order to break even or better, and I sometimes feel that this adds stress rather than making it a hobby that relieves stress from my day job. But I still have fun and like the challenges, so I will continue doing it for a while longer. But I have the luxury that this is not my main source of income, and I admire the knifemakers who take the risk to invest and try to sell their goods as a way of living. I assume that the mechanisms are similar there - you sell some and then keep investing in tools and materials - and I cannot imagine that more than a few exceptions will get rich in the process. You could not keep doing this if it weren't for the passion and the positive encouragement you get from others for your work.
Just my 2cts.