Talking about the companies as a whole (rather than just the gaming divisions):

Microsoft is far from being in a difficult financial position. They have everything... huge cash reserve, excellent profit margins (in the order of 30%).

Nintendo also suffers from the same problem as Sony regarding currency exchanges, but their profit margins are much better than Sony's so they'll still be making consistent profits (just lower than previously estimated).

You're right that some of the manufacturing may not be paid in Yen, but a big part of their staff is. What I'm certain of is that the currency issue is a big part of their worries (as is visible in their latest statements). The other part is of course lower consumer confidence (which doesn't seem a big problem for gaming right now).

That's a horrible analogy.  The PS2 and PS3 are not as different as eggs and cars.  They share the same capabilities, target the same users, (though PS3 can pick up a few Blu-Ray only customers) and compete against similar products.  Besides the arguement that's being made is that if I make X dollars with product A, product B needs to be at least as successful as product A to make X or more dollars.  Comparing PS3's success to PS2's is measured in terms of sales, more software since that generates most of the profits than hardware which contributes most of the loss at least in the early years.

Now of course Sony and SCE don't care about the previous losses, that is they don't feel the need to make up for them.  They just want to generate profits in any and every quarter possible.  But the original arguement was "A)  It's quite clear that the PS3 will never be able to earn back the money that has been invested in it..." so while they might not care, we do.  In order to do that, the fact is in the rest of the PS3's lifetime, which is dictated by consumers and not Sony, (unless they pull it early while there's still demand) it will have to earn more than the PS2 did in its lifetime.  Now nobody is saying that it's impossible for a product to do better than the PS2 did, just that the odds of PS3 doing better are quite slim.  Since PS2 was primarily a loss-leader as well, most of its profits were generated thanks to massive software sales due to it's extremely large userbase.  Sony is very unlikely to have the same advantage this generation.  Of course that doesn't mean software sales will suffer drastically as well, but they will suffer somewhat which means decreased earnings.  Then there's also the fact that development costs have risen gen-to-gen without a match in sales, a fact that hits every publisher.  Making less per unit on less units is hardly the path to out-perform a predecessor.