In August 2010 my TV did not turn on... and the red LED next to the power button kept flashing. I called my local Sony authorized repair center and they said I need to pay $299 to replace the bulb plus $75 labor.
After some searching on the internet, I bought the bulb for around $120. 3 days later it arrived and it only took me 3 minutes to install it.
WARNING - don't just buy the bulb. Buy the bulb complete with the housing which cost about $5 more but it will save you 1 hour of trying to taking it apart and putting the new one in.