There are to things about the standard Holocaust depiction that won't stand on a consistent economic analysis: 1. Mass gasing; 2. Mass cremation.
Let's think of the problem differently (Please think of this as a hideous mind game).
I am ruling over a population that consist of different races. I have a racial standard and only those that fit are to be cared of. What do I do with the rest, since they are not all the same? First, I rule them out as possible competitors. Now, I got myself stuck in this damn war and the resources grow thinner and thinner. I have to do something to preserve them while being efficient in using them. I cannot let the untermensch get out of their niche. I don't want to just kill them since it is not (yet) feasible. What do I do?
1.Let's round them up and isolate them from the main population.
2.Let's use them as cheap labour force (slaves).
3.Let's work them to death.
4.Let's try to not being so obvious about these things.
Problems to solve:
a. disease - minor dissinfection procedures, mainly to keep the ones that survey them healthy.
b. guards - minor personel requirements; select from the prisoners those who are willing to play the game for us for some comfort (+food, clothes, etc.); make sure they behave worse than our men; keep the prisoners not only scared, make them as confuse and desperate as possible.
c. dispose of the corpses
cremation is in order with minimal costs (children, women, small bodies).
mass graves - once or twice a day, based on the amount of corpses. Preferably stack them by hundreds.
dispose on site - for those working in open country; just make sure you account for them.
mass graves
*disposal of living irecoverable prisoners is always allowed.
d. food - only what is available; the camps are not to preserve the subhumans or to feed them; just make sure to profit from them to the maximum.
e. PR - not much of a problem while I keep isolating the individuals; make sure some of them escape; keep a few in good condition to testify that they were well treated.