i don't know where you live, what country/state, but where i live there is a store called joblot, they sell a 4 pack of cree screw in light bulbs for $3.99, each a real 9 watts at 2700k. the cheap screw i bulbs are great, awesome for side and corner lighting. i leave the diffusers on them, because everything i've read from legit horticulture sources says plants thrive better under diffuse lighting vs direct lighting. i've taken them off and compared with vs without, i didn't see any negatives leaving them on, actually they seemed happier if that makes any sense. the only thing is you may need to put them a little closer than cobs or what have you, but they work great. the loss in output efficiency of the smaller bulbs can be offset simply by putting them a little closer. they actually work great if i'm being honest.
edit: and as a bonus, they are safe to be used in enclosed fixtures and high humidity, it says so right on the package. pretty sweet if you ask me, it's like 10 cents a watt for cree bulbs.