How do we know when our artwork is worth anything especially money?

I don't know who the so called artist is but I am having trouble with this piece on several levels. Am I crazy? The pricing seems to be on a size basis alone and not the quality of the work. This painting, a watercolor, is about 18x20 or so and has a price tag on it of $300. Is this painting just not speaking to me and is there something really worthwhile here and I'm not getting it or is it simply an exercise in painting folds in material? I have so many negative issues with this $300. painting that I'm embarassed for it:  bad perspective and handling of the two basic objects in the frame, choppy, uncomfortable manipulation of  the medium (streaky, unflattering, inconsistencies like in the blue and green sections), object in the middle of the frame making it uninteresting with no story to tell, no apparent light source and so on. Aesthetically, it has no value, I just can't see it hanging on a wall, even in a mud room.

Perhaps the wisdom of one very learned person is applicable here. He says that he loves to write, it helps him clear and organize his thoughts, however, he would never expect someone to pay money for those thoughts, he's simply not a writer. So when and how do we know that our art work is worth money?    

If you google: painting of a raincoat. The first picture of a red raincoat comes up. This painting is seemingly simple and yet it's intriguing and tells a story . The medium moves with the painting, in other words the brush lines can be interpreted as wind rather than just filling in space. Even though the painting is impressionistic with little detail it's far more complex than the above painting. I don't have permission of the artist to give a link to the painting so I hope you will google it.

I will never discourage creativity, ever, ever! However, either on ones own or with the help of another artist (no one in the family, no moms! - sorry but they're way way too biased), we need to get an honest critique before put dollar signs on our work. I'd love to hear what you think about both images. Perhaps, I'm missing something important in the above painting.

Thanks!