There is a difference between a quick buck and a cost of hundreds of thousands of dollars for components that have little demand and aren't needed to sell the product. And that last bit is a key point, no one, and I mean no one, is going to not buy a Mac Pro over the fact it doesn't come with wifi as standard.
I don't know if it's possible to say that "no one" would not buy one, but perhaps most people wouldn't consider it.
Nonetheless, the question is, why isn't it included? If the Mac Pro is targeted for business clients, Airport could just as easily be disabled via software and be a standard feature for those who want it. Charging $50 seems a bit too much like penny pinching and the leaving out of popular features for no known reason (does anyone remember how long iBooks went without Bluetooth, or how pathetic the included RAM used to be?).
This is a business decision, and you don't get $18 billion in the bank by making many bad ones.
Nice tautology.

Not every decision needs to be a good one for a business to succeed (ie, the Zune compared to Windows or Office).
The Mac Pro isn't exactly Apple's bread and butter (I believe that distinction belongs to the macbook and iMac lines), so the Mac Pro could in fact be riddled with lots of minor bad decisions and still keep revenue coming for Apple.
Dude my point exactly...apples and oranges.
Not exactly. I know several people who never use the backlight on their iPods (I seem to be the minority when it comes to the backlight amongst my friends).
However, if you have a conceptual problem with the backlight, how about the fact that we can choose how long the timer is to be. Logically Apple could make 5 seconds a standard and remove our choice to change it. What's wrong with that?
Or how about the ability to add time into the title bar? Surely most of us don't need that since we have phones and watches. Why not eliminate that?
whereas a lot of people don't need their desktop connected wirelessly since it's plugged into other stuff anyway.
Really, so you wouldn't mind if Apple removed Airport from iMacs? The iMac is a desktop. Or do you not classify it as a desktop because it's meant for "consumers?"
Funny that I keep seeing iMacs in offices then. I thought offices only needed the wired-only Mac Pro.
It's not like it's portable to begin with. You're comparison is irrelevant and holds no water.
What does not being a portable have to do with it? There are multiple advantages to having wireless capability even for desktops.