I can't speak for an entire industry, obviously. But quality does cost. And on one occasion I purchased a highly rated - but mass produced - lens, which had such sever back focus problems that it was utterly useless for my purposes. I got rid of it and bought a different (much more expensive) lens, and have had no trouble ever since.
I am not going to damage someone else's business by "naming and shaming" - I am merely quoting it as an example of what can happen when you try avoiding the costs that go into building quality - at a level which (like Leica's) has stood the test for generations. I've never owned a Leica, so I'm not saying this for that reason. It's just that "cheaper" can easily end up not being quite such a good idea, after all.