Think the difference is how much effort your hobby is to turn it into a profitable business. 
My art is never going to be profitable as it takes me hours but I doubt anyone would pay more than $25 for it. 
But if you have prestige or enough talent to where it maybe takes 20 min you could sell it for $100 and boom. 
This is definitely true with writing as well. It can take you hundreds of hours only for your books to not sell at all.