As an electronics hobbyist for most of my life, and an electrical engineer who frequently is involved in prototyping, I am very familiar with component sourcing. Non-engineer types often have no idea where to buy the parts at reasonable prices and are shocked when they see how much parts cost at places like Radio Shack or Fry's.
There must be no product that has a bigger mark-up than replacement lamps for commercial bicycle lighting systems. I can buy a 12 volt, 10W or 20W MR11 flood beam lamp, with cover, for $2 at a local store (Ikea). Night-Sun charges $20 for this lamp, and the other commercial lighting companies aren't a whole lot better (I was quoted a wholesale price of $0.80 for MR16 lamps of any wattage). Other components such as batteries and chargers vary wildly in price, and most cyclists are not familiar with the lowest cost suppliers.
NiMH batteries have become extremely inexpensive; you can buy a pack of ten 2000mAH AA cells for less than $10, but if you go to Fry's, the exact same product sells for $20. Commercial bicycle lighting manufacturers charge very high prices for their NiMH systems.