There are several factors that determine how much a painting is worth. These include the age of the painting, the notoriety of the artist, the medium, the subject matter and the painting's status as either an original or a reproduction.
One of the first things to look at when valuing a painting is the condition of the painting. If the painting has cracks or water damage, this negatively affects its value. The condition of the painting can be weighed against the age of a painting, however. A very old painting might be expected to have some cracks or discoloration.
The painting's previous owners can also affect its price. If a painting was owned by a well-known public figure, people may be willing to pay more for it than if it were hidden away in a private collection.
If the artist who painted the work is well-known, the work will certainly sell for a higher price than a work by an unknown artist. In such cases, prints and reproductions can still be highly valuable. For example, a limited edition reproduction of a painting by Picasso or Van Gogh is likely worth far more than an original piece by a painter no one has heard of.