Everything is relative...
Well sometimes. I'm frankly disturbed by the fact that .366" bullets are often significantly less expensive than .375 bullets of the same weight, construction and style. If it takes as many steps to produce one as the other, and if the same amount of material is being used, why would one cost more than the other. If anything, you'd expect .366s might cost more, because not as many are sold, but apparently the opposite is true, and the price is higher for the more popular diameter.
Anyway, if you want the least expensive .375 ammo, you have to load it yourself, and choose the least expensive bullet you can find. For example, 16 grs of Unique over a 270 or 300 gr cast bullet, is fun to shoot. It kills small game without making a mess, yet produces sufficient velocity to kill medium sized game like deer at woods ranges. Cast bullet loads typically cost a third of what full powered loads topped with premium bullets cost, and since the brass isn't exposed to high gas pressure, or being overworked through a resizing die, it seldom needs trimming, and since the flash holes don't expand, it will last almost indefinitely, further reducing the potential cost to the shooter. I know, I know, if you wanted a .375 Winchester you'd have bought a .375 Winchester.
As you move up the velocity scale, cup and core jacketed bullets are more expensive than cast, but they can stand more velocity, they can be effective on heavier game, and they are less expensive than premium bullets. If you choose a light for caliber bullet you might get away with using a faster burning powder which has a lighter maximum charge than the slower burning powder does. There might not be much of a cost saving round for round, due to the difference of 7 grs of powder, but over say 1000 rounds, the difference is a pound of powder. Consider bullets from the former Yugoslavia. They come in plastic bags instead of nice boxes like their North American counterparts, but they are often less expensive than Hornady Interlocks, the 270 gr Spire Point is my go to practice bullet, and I usually buy them from Higginson, who still lists them for $36/50. It will probably be my go to bullet in the smaller cased .375 Scovile.
The cool thing about the big case .375s is that when you need more, you can have more. When you need it, cost doesn't matter. If you're faced with a grouchy grizzly in the willows, a testy buffalo in the tall grass, an elephant in the thorn bush (regardless of temperament) or any other African or Asiatic dangerous game which is likely encountered at close range, performance trumps cost. In those situations the cost of $10 for each press of the trigger is a bargain. If you can shoot, and if you can control your emotions, that premium bullet delineates the line between success and failure, and has to a large degree allowed the medium bore .375 to take the place of the traditional big bores, from the point of view of a client if not the African professional, although even some pros have the confidence in the .375 to prefer it. But if you choose to use inexpensive, bullets with unsuitable construction in such circumstances, and your PH is having an off day, you might not live long enough to reap the benefits of your savings. The moral of the story is, Previ .375 H&H brass - $99/100, CCI 250 Magnum Primers $4/100, .375/300 gr Swift A-Frames - priceless!
