@ condomboy
I will have to admit your greater knowledge when it comes to purchasing factory ammo.
However my skill set is quite refined when it comes to reloading ammo, especially precision fodder.
With the 338 Lapua, as long as its sturdy and well mounted, you can use conventional reloading presses, dies and tools to reload it.
Further, comparatively speaking, components are relatively common, less expensive, and the consumption of powder is at least half.
In my experience (and I have been reloading for over 20 years now) and under those circumstances reloading will save you 30-50% of the cost
depending how judicious you are in purchasing your components, and as long as you do not count your time.
50 BMG on the other hand is a whole different realm. You need much larger presses, dies, and reloading tools. Tooling up for it can cost a small fortune.
For example, to save time, and get a better quality job, I know of some individuals that trim their 50 bmg brass on mini or bench mounted lathe.
Further your components are harder to find, and many times double (or triple) the cost for a comparable projectiles and powders. Further most of the time your using at least 200 grains of powder per round.
So in that light, and in my opinion, the 338 is less expensive to run than a 50 bmg.
YMMV
regards
AbH