http://cgi.ebay.com/400-watt-HPS-HI...ryZ42225QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Its a ton cheeper than buying the entire grow light and reflector. But what can this bulb be plugged into? Only $22!
You wish it were as easy as just buying a bulb. For nearly any HID light, you must have a ballast. A ballast regulates the electricity going to light. The ballast itself is usually about $100-300 depending on the quality and whether it's digital or analog. So $20 for the bulb, say $100 for the ballast and another $30 on a crap reflector. You're not doing yourself any favors by buying everything individually unless you find some killer deal on a ballast and reflector. HID grow lights aren't just expensive for no reason