Where do unsold tech items e.g. flagship phones go?!

I was wondering if anyone knew where unsold tech items go once they are no longer the latest & greatest? (Or even not top-of-the-line, but over-produced or they failed to shift?)

For example, there is a new Samsung/iPhone flagship every year, but there must be LOADS of last year's left over once the new flagship is in stock. So where the hell do they all go? It's not as if these companies reduce the stock to shift it...

Just curious.