I think the are marked up because they can be. I have a new Light & Motion solo that is supposed to use a special bulb, but I am unimpressed and wouldn't spend $20 on it.
Some of the better bike light companies like Jet Lites and Turbocat do seem to use specially built lamps. They're still MR11s but are definitely higher quality than what you would find on batteryspace.com for example. I know because I bought a whole bunch of MR11s from batteryspace recently, and while they're certainly not shabby as cheap replacements, they are not as bright.
My light and motion solo (which is brand new) uses some sort of bulb that makes the light rays cross paths out in front of me. It is hard to explain, but basically on a dusty road at night i can see the light beams from this light actually join up, intersect and cross each other.
I see absolutely no reason for it. My cygolites on the same handlebar do not do this and they are way brighter!