Art - who decides the prices?

Art honestly confuses me. Not the viewing of it. The pricing of it. 

I read an article this week about a painting of a flag by Jasper Johns that sold for $28 million. Painting Draws $28.6 Million Bid   And I don't get it.  Irregardless of the 'special' painting technique, to me this painting looks like every crayon drawing of a flag done by every grade school student in the country.  So who decided this one was worth millions and little Johnny's is only worth putting on the refrigerator? 

How does a Warhol sells for millions and a Starving Artist painting sell for dollars?   I think Jackson Pollock's works look like the drop cloth from under a real painting.  Who decided his should be worth millions of dollars?

Seriously, is there some secret committee that meets to decide they are now going to push one artist over another?  How does one artist get labeled pedestrian and another insightful?  And who in their right mind decided that a painted circle on a painted background was legitimate art?  (On a side note, I tried to Google that one.  "Expensive circle painting" returns a lot of information about how to paint perfect circles and how to join an artists group or 'circle'. ) 

My ire is mainly triggered by pop art that looks like anyone could do it.  But even so, I don't understand how one artist's work is deemed more worthy than another's.