Uh...is this light really $429.95? And if so, why's it so great?

Lithium Ion rechargeable battery, those are NOT cheap in any respect (try pricing out Li-Ion radio control car batteries, laptop batteries, etc) IP66 rating. Takes a BEATING and smiles about it. 350 Lumens. Nothing is as bright, and it is not easy to make anything that bright, especially something that small, considering a 1 watt LED bulb produces 80-100 lumens and costs a decent sum. 3 year guarantee, INCLUDING the expensive battery. Remote battery pack, for extreme cold and weight distribution. You wanted to know why it was so expensive, you simply aren't going to find those features in a sub-$300 light, let alone one with Petzl's professional series reputation backing it up. To ErkMD, you won't see one out by years end, or in the next year, that you described, this is a very niche product. And, if your underwater with it, you don't want that brightness, it will highlight every speck of floating dust and it will be like putting on high beams in fog (unless you are in a swimming pool, in which case, why are you wearing a $400 headlamp...)

This is a very functional headlamp that chases the night shadows. Great for going fast with confidence. Some complain that it has no bike mount. Get the helmet clips and it is quick to clear the corners and turns.

It has an IP66 rating. Which means dust-proof and storm-proof. Like the deck of a crab-boat - constantly deluged, but not submerged.

Not waterproof or even water-resistant at this price? I am not sure how this even made it past marketing. Yes 350 lumens is amazing for headlamp standards, but I would hold off, I promise there will be a light as bright if not brighter within the year that is water-resistant and probably will cost about the same.

It's crazy bright, lasts a long time, and the battery pack is detachable so you can keep it under your clothes when it's super cold out. I still think it's overpriced, but those are the reasons.