Making unfounded assumptions benefits the discussion in no way whatsoever. Brummbar does everything somewhat well, but not well enough to make up for the cost and tech... especially since the StuG E does all it can do for less than half the price not even including teching and building cost, while also having something like a third of the reload time.
I don't consider brummbar to be overpriced, pretty much every time I got it recently it wrecked havoc.
Getting to T4 is the hard part, but brummbar cost and performance is exactly where it should be, it packs a punch, it takes it and can even fight med tanks so its in pretty good spot for its cost. Only issue is getting to T4.