Check them out at
www.inda-gro.com. They have 100w, 200w, 250w, 400w. The best deal is the 400w lights, you get a 10% discount if you buy 2 or more. I got a quote for $2000 for 3 400w lights shipped, I plan to use one for veg and 2 for flower. Thats equal to 750w mh veg, and 1500w hps flower.
They use these polarized rings to magnetize the argon gas or something. They have a great website. They last a long time. and are instant start, low heat, high efficiency. They have pictures of them testing them with marijuana plants too!
Also there is a thread here on RIU where someone is using 2 of the 400w lights in a 4x4 tent, growing blue dream.