It's a good point, and it's probably one of th reasons the public in general has shyed away from such lights. I mean yeah the light is amazing. However it's pretty hard to convince someone they need a $20-$300 flashlight that eats (if you don't buy on the internet) $10-30 in batteries in as fast as 20 minutes. Even if you do buy on the internet your probably looking in $4-12 per hour and in some cases in 20 minutes. $36 a hour to run a M6 at 500 lumens is spendy. But it's hard to complain about the gas mileage a ferarri gets
One of the best reasons I like the smaller lithium 123 lights is first that being lithium they have that ~10 year shelf life. I can throw one in a glove box with a extra pair of batteries and I don't have to worry every year about checking the batteries or changing them. The LX is perfect for this.
Now if your a LEO or Military person you are already carrying a ton of gear and a super bright light in a small package is lighter to carry, and they need really bright lights. Course usually there someone else is paying the bill
Even if there isn't lets face it their life can depend on that light.
That said I've found that a hour of light goes a lot longer for me than I first thought it would. Probably because I don't use the light continous, so you end up with more than a hour anyway. I probably change the batteries in my every day lights every oh 3 months (obviously I don't use it daily) so then the price isn't so bad. Probably every 6 months for my ones around the house (but I use a rechargable there).
While I really like the amazing light for size ratio you can get out of those bright 123 cell lights. I still like the rechargable ones. To me the smaller battery eating ones are more a specialty light. When you really need a TON of light or you need a lot of light in a small package. My user around the house and in the car is a rechargeable surefire. Where size isn't a big factor and the rechargeability makes it cheap to run. Those are the ones that get the most use. If I'm away from the car or the house, I use the smaller 2 cell 123 lights.
As some others have mentioned many of them carry a smaller LED light to use when they don't need a ton of light. So they don't have to use the super bright battery eater all the time
So they all have their place. I get by far the most use out of my rechargeable surefire 9N's.
Todd