you answered your own question... cfl's. if you want cheap that's your option. other than that there is hps but that's not cheap or you could use t5 flouro's (bloom tubes) but they can be pretty expensive as well. there has also been alot of talk about led's recently but i have no experience with them. you could get a 70 or 150 hps security light from home depot for 30-80$ and convert it to a remote ballast and use that. i suppose under 75$ could be considered cheap when talking about a complete hid set-up. good luck.