Here's an interesting post on Facility Solution Group's web-site about the recent volatility in lamp prices due to to the shortage in rare-earth phosphors used in the manufacturing processes for many lamps.
Says FSG in the post, "Every major lamp manufacturer (GE, OSI, Philips, TCP, Maxlite, etc.) has announced scheduled price increases that will begin on July 5th and will likely continue at monthly intervals for the foreseeable future through 2012. The manufacturers have stated they will do all they can to manage and control the price increases by tying them only to the inflationary pressure associated with the rare earth elements.
The posting also includes links to letters from various lamp manufacturers on their price increases.