If you have purchased one of the Sony 3D TV sets that either don't ship with 3D glasses or only had pair of the glasses, you can now get the active-shutter glasses you need alone.
As you can imagine, the Sony glasses are not cheap at $149 per pair. Even high-end Sony 3D TVs like the LX900 only have two sets of glasses so the family of four will need to spend another $300 to let everyone watch 3D.
Another important tidbit is that the lower-end Sony 3D TVs also need additional hardware to work adding to the cost. The glasses are available on Amazon right now.