If someone purchases some resources from owners who, without coercion or deception, willingly supply them at the price paid, and if that person subsequently (possibly after some manipulation upon them) sells them to people who, without coercion or deception, willingly purchase them with their own money, then that person has created wealth. A reasonable lower bound on the amount of wealth created is the difference between the price for which the person bought the resources and the price for which he sold them.
If an artist buys $10 worth of materials and uses them to produce a painting, and if the artist finds someone who wants to spend $10,000 of his own money on that painting, by what measure would you say the artist has not produced $9,990 worth of wealth?
I would posit that while it may be difficult to precisely value things, the fact that someone is willing to pay $X of his own money for something implies that it is worth at least $X to that person. Likewise if a person is freely willing to sell something for $Y, it is worth at most $Y to that person. I would aver that when the artist purchased the materials, they were worth no more than $10, and when he sold the painting it was worth at least $10,000. Would you disagree with those assessments? How would you assess the values of the materials and the painting?
I prefer the classic ideas of Adam Smith in the Wealth of Nations. It is a complicated discussion but in essence wealth generates more wealth. the classic example is a wetland field that won't produce anything but if I spend the money to tile it and fertilize it, now it generates more wealth every year with crops.
Adam smith disliked government, lawyers, bankers and the arts because they consumed rather than produced. He did admit they are a needed part of society but MUST not be too large or the focus of activity.
Your example of the panting is exactly what obama is doing. He believes that spending money on anything generates wealth. It is very important WHERE YOU SPEND THE MONEY.