I've seen 26W 1660/1600 Lumen 5000/6500K Bulbs sold for $6-$10. Lowes has 23W 1600 Lumen CFL for 2.48 @ that price, it's hard not to wanna use a few. Even if you don't use CFL's primarily. It's always good to have a few CFL's to give your plants a little extra coverage! Shit, my setup now is all CFL's (HPS ARRIVES IN THE MORNING) and i've got 20 inch plants that look pretty good.
Using something like 13 of those bulbs. So 32.50 @ lowes for that, and I have a few more of the 26W ones I had from before I found them @ Lowes. so, 18 total if you count my 1x 55W 2300K CFL, I just switched to flower and and letting them flower their first week or so under the 4x5000K, 13x 6500K, and 1x 2300K CFL's (Put's me just under 34,000 Lumens and @ about 460W's, which personally is why I think MH will work better next time around, for the same wattage you get many thousand more lumens, but not the same coverage!), the 2300K was simply a way to get it used to the change in light spectrum (not needed I know), and give it usable light for it's change into flowering.
Sorry, got off topic...
My point being, cheap CFL's @ Lowes as well...not even close to that cheap. But i've seen the bulbs @ Costco, they usually don't label the Temp on it (ie; if it's 6500K or 2300K). So I never personally was interested. I could tell you what it was by looking @ it....but i'm not buying it under those conditions.
Anyway, good growing to you all!