expensive/good mics basically pick up more detail and clarity as well as having lower self noise. It's impossible to EQ in detail.

I wouldn't always say the winner is the expensive one, like a bad mic used well is always better than a good mic used poorly. Weeelllll sometimes : P

But my understanding (and I possibly think this just to sleep better at night) was that the reason you can't truly just process sound from a cheap microphone is that it may have not captured those frequencies in the first place. Or at least not in the same way. So by trying to bring those characteristics out, your enhancing certain aspects, likely the bad along with it.

That and of course the physical components may differ greatly, meaning colouring in the more expensive mics will be closer to what we hear on a daily basis and be what we class as more professional. Plus we need to keep thinking this was, or else who would make money making heart breaking & expensive mics.

The membrane is an analog device. It's operation varies continuously. Thus, you cannot change the overall recorded signal to sound like what another microphone would have picked up using static post-processing. Regarding noise, different microphones also have different noise prints. Different microphones also have different housings, which affects how the signal is directed to the membrane (reflections and phase cancellation occurs). There's just so many variables.

I don't think it's a question of cheap vs expensive nowadays, at least in studio microphones. It's just good design vs bad design. You can find many microphones with good design for cheap nowadays, although the used inventions are likely ripped from expensive microphone designs (e.g. Neumann). It's just the manufacturing that's cheap.

In field-capable microphones there's much less competition and less cheap copycats.

basically, get a U87 and a cheap condenser, make a 'hissing' S sound into each and record the results. you'll have your answer.