Actually just the bulb is $18. The rest of it I scavenged from junk. I wanted to make some new lights for starting seeds.
This is the bulb:
http://www.menards.com/main/electric.../p-1856945.htm
It's a 65W, which is 200W equivalent, in "Cool White," 4200 Lumens at 4100K. Menards had a 300W equivalent, but it was in Day Light and not Cool White.
I had an old socket, but a new one is $1.71 at Lowe's:
http://www.menards.com/main/electric.../p-1856945.htm
The socket will take any normal bulb. The 150 watt equivalent cool white spiral CFL is another decent choice; it's about half the price. I wired the socket to an old cord from a computer monitor that died. I made sure to look up the carry capacity of the wire, but I am only running it at 10% of it's maximum load.
The socket is attached to a scrap of plywood with a hole cut in it from a hole saw so the bulb can poke through. My reflector is a plastic Rural King bucket cut in half. I used an oscillating saw to cut the bucket in half. A hack saw or coping saw would probably work, too.
http://i.imgur.com/4V4Kwkg.jpg
http://i.imgur.com/iPSxrM2.jpg
http://i.imgur.com/5rubq5P.jpg
By buying just the bulb and making everything else, the light ends up being 1/2 to 1/3 the cost of buying a pre-built grow light.