Apologies for all the real world examples coming, wasn´t quite intended at start.
This became one very haphazardly written and overly random looking post for some reason...
How much of your economy you are willing to dedicate to the military. Europe fights to get 1.3%, the US does 3.8%.
Though USA is pretty much bankrupting itself with that despite exploiting the petrodollar to massprint money that in any normal economy would cause hyper inflation.
A decently functional economy can usually handle 2% without much trouble.
You resources available to provide raw material to build stuff - in the honorverse this is pretty much not an issue.
Mostly isn´t. It can be. The basic fact that raw materials tends to be taken where it´s easy, means it´s often easy to raid against such operations, and if a nation looses a lot of mining operations, no matter how insignificant each one is, it´s going to hurt eventually. Of course, a sane nation will have mining ops outside of just outsystem asteroid fields and such.
How expensive your equipment is. The US tends to gold plate everything, so we have very, very expensive ships and aircraft that are usually pretty capable (other then disasters like the LCS)
And the F-35. Last joke i heard about it was that it´s going to cost as much as the F-22, at a quarter of the capability.
Moreover, it´s the degree of corruption and political porkbarrelling that adds much of those "gold plates".
And a handful of idiots who seems intent on making the specs for anything requisitioned to get bent beyond silly.
Anyway, you might say this is part of the "overhead" costs for items, and this adjusts what is possible quite a lot.
You find almost none of that kind of corruption here... Which gives:
Comparison, SAAB-39 Gripen, cost per flighthour ~4700$ peacetime nonoptimised, F-16 7500$ optimised, F-35 >32000$ wishful thinking.
Groundtime per flight:
Gripen, 10 hours with 2 technicians, can cut turnaround with full service to less than 2 hours, mostly by merely using unskilled assistants.
F-16, 19 hours with 6(?) technicians, can cut fullservice groundtime to less than half that.
F-35, 20 hours claimed, 23 hours apparently for real, with 17 technicians and "assistants", theoretically able to get full service in 12 hours, but that seems to be with at least 4 full service crews working on it.
How expensive your military personnel are - large conscript militaries can be pretty effective, but are not normally as effective on a per person basis as a long-service professional force.
That depends completely on HOW the force is trained and maintained.
Conscription has the huge advantage of being able to pick, choose and pidgeonhole all recruits towards they are hopefully best suited for.
A military recruiting small numbers over time has less leeway, they simply don´t have enough of a selection to be able to put people where they seem best suited, they have to put them where they currently have room.
Example, my friend who is insanely good at organising? He became a logistics specialist. Another friend with good kinestethic sense, pilot. My cousin good with animals and superb physique, a dog handler with the airbase rangers(the folks trained to find and hunt down special forces), my dad and brother communications and cryptologist, again things they already did before(anyone who knows the term DX-ing will understand why), my older brother a mortar battery commander as he is a natural with trajectories(never ever play Ballistics against him!)...
Compare that to people i know from "professional" armies in other countries, at least 1/2 of them end up somewhere they´re not suited for.
Willingness to fund training - good training burns out equipment, gets people hurt and costs a lot of money. Many militaries simply don't do this.
And more the woes to them!
Money spent now is lives NOT spent once fighting happens.
Even if this isn´t 100% comparable with Honorverse because of how good and available their simulations are, there´s still a million things to teach just about everyone.
Anyway, as already noted, the biggest baddest bottleneck pre-war for Manticore certainly seems to have been political. OTOH, would they have fared as well as they did with a larger less well trained force? Maybe.
But i very much doubt that they would have been able to reach their technoligical heights if starting with that larger, less trained force, as the total force size would increase cost of ownership, while political restraints would keep total expenses from rising too much, hence reducing the ability for training.