So great to see this article on affordable art. There is, without a doubt, an abundance of talented, independent artists selling their work for cheap. It's just a matter of helping people to connect and find art that resonates.
I'd also recommend the following galleries which all have online presence:
https://www.enormoustinyart.com/
http://fontanellegallery.com/
http://www.thinkspacegallery.com/
http://www.tinlark.com/
http://www.magic-pony.com/
http://www.beholder-art.com/
http://www.lebasseprojects.com/
http://www.hibbleton.com/
http://www.soovac.org/
http://raredevice.net/
http://sebastianfoster.com/