[laughinghan]

I think your points 2-4 all make sense, however:

    1. What do you mean by price?
    1. Price is hard to figure out. Do you want to sort by the
    base price of an item, the price plus shipping (which
    depends on where you live), or the price after discounts
    or specials? What about products that are sold both by
    Amazon and third party sellers, where the 3p seller
    charges less for the item but more for shipping than
    Amazon? Which price should be shown?

What possible reason would we have to care about the "base" price before shipping, discounts, or specials? When I say sort by price, I mean sort by how much money my bank account decreases by, and I think Amazon already knows this, because when you look at "New" or "Used", it sorts by base price+shipping, just like it should.

That being said, the other 3 reasons sound intractable, and are exactly the reasons I would have guessed.

[davezatch]

Except that shipping is not necessarily obvious. There are several options (overnight, 2 day, longer) with different price points. Also, if you're a Prime member you get free 2 day shipping, but what if I'm prime but not logged in/using a different machine?

And setting a default shipping cost is likely to further confuse customers. E.g. if you show the cheapest option always, there will be a price bump at checkout, but you don't want to show expensive option by default because it raises all perceived prices.