So there is this thing called the invisible hand which works its wonders via supply and demand and the technology curve. New technology is expensive and costs a lot right when it comes out and supply is low and demand high. As the supply increases and the companies make back their research money prices go down. As new technology hits the market demand decreases for old technology and the prices drop even more.
I thought they still taught Econ in school...
Add in the explosion of legal states which increases competition and boom, even lower prices. And everything is getting cheaper, not just ballasts. Hoods are cheaper, fans, filters, ...