Why should there be an upgrade price? Simple, it's an incentive to try and get the user to replace software they already "own" and that presumably works just fine. (Heck, even with upgrade prices there are a lot of people running Office 97 on Windows 98.) This reason doesn't really apply for the examples you cite (in my experience).

1. Television - Don't know about you, but I don't buy a TV as an upgrade. Looking at my past purchases, they've either been replacements for broken units or second units to put in another room.
2. Microwave - Only purchased to replace a broken set.
3. Shirt - Could be a replacement for a worn-out shirt or (more common) an extra shirt. I don't think I've ever really "replaced" a shirt.
4. House - This is closest to the software scenario. All of my moves have been from one livable house to another. And guess what, on all but the first I got a price break by selling my old house when I bought the new one.