[b]ningonango[/b]: Whether or not spending the $$ on a particular rifle is purely up to the owner. I did some research between the .50b, .449LW and the .458 when I was looking into a big-bore AR and just felt that the .458 had more to offer [b][i]me[/i][/b]. If cost is a factor for you, then perhaps the .50b is a better cartridge. (Don't forget to look at all the niggling details like magazines, ammo, etc.)
I think each has it's downsides:
50b - modified magazines, possible limitations under recent .50 cal bans
.449LW - proprietary mags, ammo/reloading supplies only available from the manufacturer
.458Socom - ammo only available from Cor-Bon, reloading dies needed to be custom ordered
On the plus side, to me anyways, Starline Brass is now making quantities of the .458, Cor-Bon has begun shipping ammo Lee made some dies for us here on the board and I can use ANY/ALL of my existing USGI 20 & 30 rd mags. It's taken a few months, but everything is falling in place so this cartridge worked out for me. It may not for you. I was merely offering another perspective. (Note: I think the AR-10 is another viable choice as I know a lot of people who use .308 for big game hunting)
If you want to look at my .458, here are some clickable thumbnails. I've got pics over on my unofficial [url=http://www.mylittlespark.com/ar15/458Socom.html].458Socom page[/url] - basically a place for some of us to share our reloading data.
[url=http://www.mylittlespark.com/ar15/images/458-01.jpg][img]http://www.mylittlespark.com/ar15/images/tn/458-01.jpg[/img][/url][url=http://www.mylittlespark.com/ar15/images/458-03.jpg][img]http://www.mylittlespark.com/ar15/images/tn/458-03.jpg[/img][/url]
On a side note: Kaliban/Kalifornia are tongue in cheek (or maybe not) references to recent California gun control iniatives that remind people of a certain idealogy that caused a little mayhem in Europe in the '40s or the middle east in the '00s. Rincon was specifically referecing California's ban of .50 rifles.