Quality, consistency, strength, case life etc. etc. As far as I'm concerned they are worth every penny. You just can't get them for every chambering/round.ge(
If you don't look for the best in all of your components then you could probably get by with WW or Rem or whatever. The choice is up to you but even though brass is an expendable component that eventually wears out, it's one that can make or break you at times so why not spend a little up front and know you have the best?
It is so desirable b/c it is the best brass made. Lapua, like every other brand, has turned out a bad batch or two, however, it is the best brass overall and many would say Norma is as good or a close second.
Consistency and quality are the best things about Lapua. Flash holes are cleaned and don't need to be reamed. Case neck thickness are very consistent as well (most I have measured have been a difference in 0.001") so brass doesn't have to be neck turned to be uniform in a no-neck turn chamber. Case walls are thick in the body where pressure is exerted. Most brass in annealed at the factory to provide a great case neck tension. Price is also great compared to other quality brass manufactures, where Norma charges about +50% more compared to Lapua brass and of about the same quality. I myself have gotten over 10 firings through my brass and it's still doing great, they should be annealed at or slightly before that point though.
It's the best priced and quality brass all around, you really can't go wrong with it.
The same thing that makes RWS brass so desireable. Closer manufacturing tolerances, tough case heads that allow higher pressures to be used compared to WW, Rem, or Fed brass prior to expanding and loosening up the primer pockets.
I think RWS brass is actually tougher than Lapua, and will purchase it preferentially over Lapua when I am able to.
Lapua brass is more consistent and uniform, case prep is minimal to non existent and case life is exceptional. I got 16 firings from a batch of .338 Lapua brass I was using. Primer pockets were still tight even though some of my loads had been pretty hot. I finally had to discard them b/c they had swelled slightly just above the web and F/L sizing would not allow them to chamber easily. If I had small base dies they may have still been useable.
I retired some .308 win. brass (also Lapua) after 25 firings.
If they were available in every caliber I would use nothing else. I have not tried RWS brass so cannot disagree that it might be as good or better but Lapua is the best I have used by a wide margin.
Norma brass is good but softer and will not last as long as Lapua.
Try some in one caliber and see if you like it. The price is the only thing not to like but it is well worth it.
"Fenced yards ain't hole cards and like as not never will be, reason for rhymers and old five and dimers like me."