Gee, wiz, that sure sounds like alot! But not really. This sounds like a tiny fraction of the effort it takes to produce even one physical copy of a book.
Umbran's suggestion about limited manpower is good, except that this isn't a case where WotC could do only one or the other.
The profit margin of PDF sales is higher than dead-tree copies. Period. I have to assume their removal wasn't about the profit they might or might not have provided, it was some convoluted and stupid market strategy to prop DDI and the newest edition.
Higher profit margin or not, you're still presuming that WotC's revenue from selling PDFs was significant enough to outweigh the fixed costs of doing so. Since WotC has still not resumed selling PDFs, the most logical explanation is that it isn't profitable for them to do so. Therefore, I have to ask, why is your "logic" leaping (at the point I've underlined above) to the assumption that WotC isn't interested in making a profit?
Also, in your OP, you said you don't want this to become a discussion about 4E. That said, why the veiled attack on D&DI and 4E, by suggesting that they need to be "propped" (up?).
Um, it has what, a couple dozen salaried employees? At best? I may not run a business of such a size, but I am employed within one that dwarfs it. And yes, it's not a publishing company, but I think just waving your hands around and saying "it's a business!" is a copout. It's not like WotC is some mega-corp with inscrutable goals. It's a small publishing company.
...So, you're saying that smaller* (ie: medium-sized) companies don't need to behave as businesses?
Why stop selling old products in the first place? Why take the stance that old sales necessarily negatively effect new ones? Is there any evidence that Fallout 2 is stopping people from buying Fallout 3?
Well, to make one suggestion, WotC likely isn't interested in splitting any of its resources to support both its newest product line and an obsolete product line still being directly supported by its competitors. I'm speculating here, of course.
It's worth pointing out that once Fallout 3 was released, it's unlikely that many new copies of Fallout 2 were still being produced. Maybe that will change in the future, but who knows?
The front end costs of selling older editions material have already been payed. The books have been produced, the PDFs have been made. And even with 4th edition, the books are printer proofs before they are hard copies.
I'll point out, too, I was an avid MtG player before WotC's actions, and now I don't buy them.
Goody. I can appreciate you "voting with your dollars", but I don't think your reasons for not wanting to support WotC are very legit.
I'm not going to buy that simply because it's a business, WotC's decisions can't be questioned or contradicted, nor do I believe that doing so requires a PHD and 5 years of industry experience.

That's a double standard that doesn't apply to incensed customers, apparently.
You're right, anyone is entitled to question WotC's decisions. That said, most of the reasons you've offered so far don't appear to hold much water -- only nerdrage.
Upthread, I pointed out that "publisher wars" are the kid siblings of edition wars. Since you don't want to buy anything from WotC, but you also want to tell everybody about it, I strongly suspect you're looking to start a "publisher war" -- in other words, you're just looking to drum up hatred for WotC. (Trying to generate hatred against Paizo would be just as bad.)
So, I'll just reiterate: I don't like what WotC has done and will not buy their product until their policies change.
Great! So don't, then. ...But why are you still telling us about it? If that was all there is to it, we wouldn't be on seven pages of discussion by now.