There is no such thing as originality.
The crux of ones being is a collected identity based on experience and influence from birth to death, there is no grand narrative and no whole. We simply exist through experience and episodes.
Wow. I love it. I love how you've got the statement that everything is not original, a product of everything, and put it on there like an an advertisement, as if you're trying to put the ideas of postmodernism to us, yet still questioning the idea by suggesting that postmodernism is simply consumerism. I don't know if that's what you intended, but that's what I got from it.
Your logic doesn't follow. Your concept is good and your conclusion/individual statements are correct but your reasoning is blind at best.
People experience different things and experience similar things differently. Since everyone does not live out the same things in the same way, the sum of their experiences (aka themselves) are different if even by slight nuances. Originality does not have to be abstract (i.e. achieved from nothing) because everything cannot come from nothing (zero =/= infinity). Originality is defined as something different and we are all different if we count every factor in the equation of ourselves so therefore everyone is original in total.
I agree with everything you said that does not contradict the logic above.
Being different sums is precisely what makes us different however we are the same in being different sums. That's why originality is banal.