That just goes to show that you don't have enough incubator capacity. If you had room in the incubator to hatch as many chicks as you can sell, and had extra room to put your own project eggs in, the cost per set goes way down.
True case: I have 2 roos over 120+ hens. Fertility as expected is pretty low in the Red Sex Link hens, there are a few that are submissive, others play hard to get, and the roos can't keep track of who's been caught. The Easter Egger hens, on the other hand, number under a dozen and the roos get them all. I set 96 eggs for my Easter hatch, two day's production of hatching quality eggs (no dirt, no irregular shells, no porosity, best color, best shape, etc) and only 19 were fertile, 4 of those brown, All the greens were fertile. Overall, that's only a 20% fertility rate. My cost to put these low hatch rate eggs in the incubator was the retail value of the eggs, $32. So each chick cost $1.68. Think how much better you'd do at 50% hatch if you were using surplus incubator space.