When Maud was alive, she sold her small painted cards for twenty-five cents each. Last year, one of her paintings sold for $22,000 CDN (a little less than $17,000 USD).
Here's the trailer to the movie. Sally Hawkins and Ethan Hawke and Maude and her husband are wonderful (aren't the always?), and I highly recommend the movie. I wish I could find a book on her life, but there are a number of articles about her on the internet.
Here's a link to her page at the Art Gallery of Nova Scotia and a link to a site with more of her art.
Now I'm off to look for more on Maud Lewis. What an inspiring individual!