In this case, the artist does not have an established auction record to show that his market is willing to pay in excess of $20K for his works. As an artist, he would certainly like to price his works at that level and a collector would purchase such as a speculation without guarantee of return on investment. It is unusual, for the most part, in the art market for a painting done during schooling or academic studies to sell for higher than a work that exhibited after the artist has established themself in the market after graduation. As the owner of the work yourself, you have the privilege to ask any price you want for an item you own; the key factor is finding a willing buyer at your pricepoint. You may want to try to sell this through ArtBrokerage.com. Art galleries tend to sell only artists on their roster. You can also try to consign the painting to an auction house in a large city near you; that will help to begin to set an auction market for the artist himself, however it would not be likely to achieve bids near $20K.
Please let me know if I can be of further assistance on this painting for you.
Since there are no precedents on auction sales, then the value is what someone will pay for it, and that can be whatever price you place on it. Value in the art world is perceived and not absolute. To the artist, the perceived value of his own work is $20,000+. Based on the general art market, the auction value, with no preceding record as a benchmark, the sale value (if you you were not to set an asking price yourself) would be under $400.