When buying art, it is important you know its value and why you are buying it. If you are buying just for pleasure or decor purposes, you don't have to concern yourself with value. If you are buying art with investment on your mind - be careful. The market is currently saturated with art, old and especially new. And many art owners are learning the art they thought they would be able to sell with profit are not only selling below profit, but often not at all.
Many new to art buying are purchasing art from artists who are young and less experienced. These artists often do not have a well-developed secondary market for galleries and dealers to use for valuation, rendering their art a huge gamble.
However, if you buy art from a new artist with long-term investment in mind, it may prove profitable. Maybe not for you, but for your children or grandchildren. In this case you should view this type of art as a long-term gamble. Think of the buyers who bought Monet and Renoir's first works... 😁
Art from an established artist with a re-sale secondary market is the best way to go when it comes to "safe" investment. This usually requires more money. But you are paying for relative assurance. .
To determine numbered value, please do not limit yourself to what galleries are selling a piece. Galleries sell at retail price. They can price art according to whatever business model they follow. Generally, it is best to get a second and maybe even a third opinion from an art evaluator to make an informed purchase.