If you can afford the ammo, go for it. You have checked prices haven't you? Reloading will help but last I checked, even that wasn't very cheap.
I shot the AR-30 and the AR-50, I love both but when it comes to realistically using either enough to warrant the purchase, I have to admit that with all my other firearms, they'd collect dust. I am flirting with the thought of getting the .50 though, just to say I have one without having to spend 8 grand
i almost nabbed a Barrett a few years back, wow would that have been a mistake. Awesome rifles but for several grand less, one can have just as much fun
The AR-30 in .338 shoots like a dream. That muzzle break is hands down the most efficient ever made. It better be, it's huge! Being the shooter, the sound level isn't bad. Switch roles and be a spotter or someone just hanging out and you'll notice just how loud that beast really is. The AR-30 doesn't look fancy but the groups you shoot will put a huge smile on your face. Very accurate rifle if you do your part. I have never heard of ANY of them being anything other than very very accurate out of the box.
I wouldn't bother unless you're into long range hunting/shooting. You'd be doing a disservice to the rifle and the caliber. That caliber was made to reach out, I mean reeeeeeally reach out and touch someone and/or something.