perhaps, as i'm thinking about it
if you had a use for say Industrial Eq, which comes in many varieties. How ever, a bran new tractor, will cost 100K or more, for good quality. a low q, or used tractor, would be half the cost, and allow you to preform the same job. And perhaps, higher quality services, that would be, better operators, and mechanics, would compensate, and keep the EQ running longer, and at a higher performance level.
unless you can figure out a way to buy cheap goods from your CM, the only way to get them, is via world market.
the problem with buying cheap goods via contract, means that you have to tank a corp to produce lower Quality, how ever, do to the game machanics, low q corps, just don't make money. hosing a one corp to feed 20ish corps, would be cool, but when your talking things like FMUs, you'd need one for every 6ish. so just trying to keep the low q FMUs via contract, you're hosing 1/6 or your corps. and thats just FMUs, that says nothing for EP, or some of the other stuff you'd want low.
an alternate suggestion, would be to allow players to run their corps like normal, but exchange High Quality, for Higher Production of lower products. Like a Cars corp that would otherwise produce 240Q, could instead, produce twice as many 120Q cars, with the supply, upgrades, and salaries levels. i mean, giving the option to the player to adjust that. i've suggested that before, but it got ignored. its one way, but again, its something that talking to the GM might be best.
problem with your thought process, is that cost, is still cost. regardless of the source. if the source in in-house, then its still a cost. and if you are buying higher than usable Q, its money you are spending, with out any benefit. You wouldn't expect a 20M Diamond necklace to go for 5M, just because it was made locally? No, the maker of the necklace will still want his 20M, regardless of the buyer. If the buyer would prefer a 5M necklace, he should look for cheaper product. Which may be of foreign origin!
as far as some products not really being realistic to have a Q level, like EP. well, i wouldn't say your right, but you do have a point. thats one of those things that I ignore, do to this being a game, and therefore imperfect.