Start up price, only a 2.5ft spread...so for any large area is would cost like 4*450 and thats just a 5x5... when one gavida provide decent PAR in the same space for the same price as one. Some people in the winter use the heat for their home so its not as bad money wise.
But still... better umol/j for a cheaper price? Cobs are just the best answer currently. would you rather pay 1800 for 1200W at 2.08 umol/j (2496), or pay 1200 for 800W and 2.6umol/j (2080)?
More power, more efficient, more good.
Long term I think the numbers work them selves out pretty well. Im not sure if the above was at the in reference to only the CD binned 3500K, but Im running DB 4000ks and thats a bit more I believe.