I buy metal frames from

https://www.framesbymail.com/

An economy metal frame size  8x11  is approx $6. They are in MO but I dont know if they charge less if you're closer - they charge 13.5% for shipping but min of $6.95.

They will also do mats+ backing+ Plexiglass if you need it.

I havnt found anything cheaper locally (Denver)

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
http://artpearl.redbubble.com/