I own a Savage 110BA and I really like it...
That said, I don't think the 50 BMG would cost any more to shoot, really.
The factory ammo for the Lapua mag is about 5 dollars a shot, and reloading it costs around 1 dollar a shot.
You can get surplus 50 BMG ammo that is often pretty good stuff for 2 or 3 dollars per shot, in reloadable brass...
50 BMG powder can be bought surplus as well, so if you do a little figuring, I think you'll find that the 50 is just as economical to shoot as the Lapua mag... maybe even *more* economical if you buy surplus components.
And Barrett versus Savage? I'm a Savage guy, died in the wool...
... but the Barrett will hold all of its value, and is a beautifully made weapon.
Dan