You have to compare like with like, if you want to perform a useful comparison. One of the problems with the light comparisons on this site is the constant switching of topics-- from cheaper per lumen to "brighter" to "more convenient or whatever. The discussion here is informal, so this is to be expected, but to get the best overall picture you really do need to keep in mind that there are various factors that matter to riders and different kinds of commercial lights represent different tradeoffs of those factors.

Now, it's possible to buy a *100 watt* halogen spotlight for under $40. That thing is brighter than any HID bike headlamp commercially available (though not as bright as the HID spotlights). It's a lot brighter than your car headlamp. So, obviously it's possible to generate more light per dollar with halogen than with HID.

Of course, the spotlight weighs at least seven pounds, has a reflector the size of a dinner plate, and has a run time of about 45 minutes.

The point is that when it comes to bike lights, lumens-per-dollar is not the only important consideration. Space and weight are at a premium on a bike, so those things matter, too.

HID lights give you much more light per unit of weight and volume than halogen do. But they're more expensive.

These facts can work themselves out in a variety of ways. If most cyclists didn't mind lugging around all of the weight Steve Knight carries for his halogen lamps, it would be possible to have HID lamps that put out staggering amounts of light. Such a system would be a *lot* brighter than halogen lights connected to the same power supply.

The commercial HID lamps seem to think that riders look at things differently. L&M seem to think that the 675 lumens their ARC puts out is enough for most riders, on or off road. So, their lights are a lot lighter, more convenient to deal with, and have a longer burn time than halogen lights that put out the same amount of light at at time. Again, reducing these properties compared to halogen is possible because of the basic fact that HID provide more light per unit of power than do halogen lights.

If you don't care about weight, size, and convenience, then halogen have no disadvantages compared to HID. But most people do. So, using halogen will result in some disadvantages for most people.

On the other hand, halogen lights are significantly cheaper than HID lamps.

I don't know what to say about SK's charger claims and all that. If you look at the commercial lights, though, the high end halogen Jet Lites are a decent comparison to the L&M ARC light. I don't have the time to compare them in detail, but if you do you'll see the fundamental facts of lumens-per-dollar and lumens-per-watt reflected in their relative advantages and disadvantages. The Jet is probably brighter at its very brightest, but it has a much shorter run time at that brightness than the L&M. The Jet is heavier, all things considered, and takes up more room on the bar with its lamps. But the Jet is cheaper.
And so on.

Halogen bike lights would be an even better bargain if higher end rechargeable lights were in greater demand. The halogen spotlight I mentioned earlier can be bought at sporting goods stores. $40. If rechargeable halogen lights were popular enough to be sold at WalMart, the way spotlights are, they'd probably be about half the price they are now.