that depends on your set up, tent size, amount of cobs, drivers etc... but for a 3x3 tent with lets say 4 to 5 citizen 1212 (cheapest on the market and still perform well, it what I use) and a driver plus frame, bits and bobs your looking at around a £300 to £350 start up for a basic set up. I would say that's about the same in $$$'s. It seems like a big spend but I must have reaped the money back in electric over this passed year.
With the tech now catching up, generally cobs are out stripping HPS in many area's especially in yield and trics, not so much in bag appeal (that's all hps has going for it self these days on the pros and cons)
What I can recommend is to immerse yourself in Growmua5 vids on youtube, watch them over and over to get the understanding of the LED diy world. With out them my 2 lights would not have come about. here the link dude.
