Easily done for less than $10 a box with quality jacketed bullets, even at current prices. I overpaid for Federal Match primers, just to conduct an experiment. So primers 4.3 cents, bullets 10 cents, cases essentially free...yes they cost if you buy them, but by the time you’re on your 6th load it’s less than a penny. Powder...an expensive pistol powder will still only cost about 2.5 cents per round. ($38/7000)*4.5gr = $0.244 for Vihtavuori N320 1 lb bottle. So 4.3 + 10 + 1 + 2.5 = 17.8 cents per round or $8.90 per box of 50. Every one of these costs can be improved. However, substitute the bullet for a high quality self defense projectile, and you’re still loading a box of 50 for the same cost as a box of 20 self defense rounds.
Check my math.
Now, this presumes that you don’t charge yourself labor, and the equipment is a sunk cost. Try amortizing your equipment into the equation, or paying your labor cost, and it cannot be done for less than factory.