Paper glasses cost pennies to manufacture. You can get a pair for 40 cents from American Paper Optics, as long as you purchase at least 50.

RealD creates black frames for various uses, like this pair for adults...

...this one for kids (for cinema handouts)...

...and this one for professional use (medical research or product design--this pair costs $450).

For the 3-D fashionista, Look3D creates $25 3-D glasses that mimic designer frames. Glasses from their handmade directors collection go for $100 per pair.