so I sketched my plans, invested and cashed in some friend-checks, and now it it is built.
This is what I use today when traveling down to the really big caves with the heighest ceilings :) and it works perfectly!
on request I made my own small instructable to take interested people through the process.
looking back on the costs of making this lamp, I managed (hand on heart) to get it down to:
LED´s - 25$
Buckpuck driver - 30$ (shipping included)
Battery case - 3$
Some new batteries, 4 of them - 28$
The casing was for free - YES! YES! YES! - thx Robin!!!
which bring the cost down to 86$. I would say a GIGANTIC leap from the 300-400$ pricerange of a more serious headlamp from for example Petzl, Silva or Black Diamond.
And it really really REALLY does deliver the same amount of light as they do.
The only drawback might be that the batterylife for the expensive ones is longer, but if you switch up from standard AA to LIthium batteries ( as I will do ) you should get even more for the small amount of money you put into it.