This is true. Although I would add that the knock off items are a bit of a crap shoot. Sometimes they work well, sometimes they don't. I bought some knockoff stove knobs a few months back because the old ones were stripped and would fall off. It's been 4 months and knock on wood, they're still as good as new. It would have cost me $120 for new factory originals, but I got the knockoffs for $30. In this case, the price difference was just too much, but the cheaper ones worked well enough.
That said, this wouldn't be the same for a lot of products where you wouldn't want a knockoff.