There's a huge misconception on how expensive they are to shoot. 50bmgis expensive, even if you reload, because of the sheer size of everything. I reload my match quality 338lm ammo for $1.25 a piece. That's not skimping on anything, I'm talking about Berger bullets and lapua brass.
People that don't reload and use factory match ammo,pay that much or even more per round for their 308!
Also the other reason for it vs the 50bmg is it is inherently more accurate round at long range. I've shot mine to 2200 yards.
If you need energy on target, then 50's where it at, otherwise 338 is the clear winner.