The value of a Lee Reynolds painting can be determined using the same process as any other work of art, by analyzing certain aspects of the piece, including condition, subject matter and rarity. These are compared to auction market standards to find an appropriate price.
In order to value an artwork, the seller or appraiser must evaluate similar works and their sales prices. It's especially important to find these comparables if the artist in question has sold a large number of works at auction. In these cases, it's easy to find an average price for a work fitting certain parameters of size, medium and subject matter.
If the artist has not sold many works at auction, this indicates that his work has a high rarity. However, this is only a good thing if there is also a lot of demand for that artist. Even an artist who sells a lot of art might be in high enough demand to still be worth a lot of money. For example, there is great demand for the works of Picasso, so even though a large amount of Picasso's works sell at auction, they are still priced high. However, works by Picasso from his Blue Period are even more expensive, because they very rarely appear at auction
Lee Reynolds, whose real name was Lee Reynolds Burr, was one of the first artists to explore the mass production of artworks. At his Vanguard Studios in the mid 1960s, he allowed students to copy his paintings and sign them as "Lee Reynolds." These paintings usually depicted inoffensive, even banal subject matter, and were painted specifically to sell to a mass market. All these factors mean that paintings by Lee Reynolds are neither rare nor in demand as of 2015, and are therefore not worth very much.