Cheap 3D cinema exists !
3D cinema as low as 3$ is possible !
Regency's Valley Plaza in the North Hollywood area offers 2D movies for $3 ($1.50 on Tuesdays), all shows all times and 3D movies for 5$. All theatres are film only, not digital but they converted one mid-size theatre (220 seats) to the Technicolor 3D system (35 mm film based projection in over/under format) That makes 3D price $5; $3.50 on Tuesdays. Limited selection for 3D film prints. They played Captain America for six weeks and are now playing Three Musketeers.
About 30 miles south, in La Mirada, there is a Starplex discount house with three Real D theatre screens that have played up to 5 3D movies at the same time. Their prices are: $2 for 2D, $4 for 3D; Tuesday prices are $1 for 2D and $3 for 3D.
Thanks to John Christopher for the tip.