Ah, see, I had hoped you'd be sensible enough to recognize that my question was an obvious bait, but I see that's not the case.
In that case, I am sorry to inform you that what you have just described is not unethical. An "unethical" action is one which inflicts harm upon society or a subset of society. Video games, however, are luxury items. They can be freely sold or denied to customers at will, with no actual detriment to the society at large or to any portion of society.
"Unethical" is a company dumping sewage into the town's drinking water. "Unethical" is a corporation using its money to bribe politicians in an effort to push for laws that benefit them and harm their competitors. "Unethical" is most certainly not a word that can be used to describe DLC. It's no more "unethical" than expansion packs before them, or game sequels. I would agree that it might be bad business practice, but it is certainly not unethical.
This is like walking into McDonald's and ordering a cheeseburger, then expressing moral outrage at the fact that they refuse to serve you a Big Mac instead. Or getting upset because they charge you extra to add certain condiments. You purchased a cheeseburger, so you get what you ordered. You do not dictate what that cheeseburger contains, the company selling it to you gets to decide how much to charge and what it contains. If they decided tomorrow to cut down on the contents of their Big Mac sandwich, and instead offered you the ability to "upgrade" the sandwich for an additional fee, you might moan and complain, but it's within their right to do so. It's their product, and it's a luxury item, so they can do whatever they want with it. If you don't like it, go get a burger elsewhere.
This is hardly a matter of ethics so much as business practice. And I can honestly see why they're starting to make the shift towards a model like this: because making games like this is expensive. Consider that if such DLC was not present, it usually means that the development team is either moved to other projects or terminated outright. It usually means that the costs of the production are harder to recoup. Now, my natural response to that is "then stop spending millions to make your games and start being efficient" because I think it's poor design, but I can see WHY they're doing this sort of thing.
The capstone to this argument is perhaps this, though: everyone in here arguing about how the character is essential to the game's nature, and how it simply can't be denied to them, hasn't realized that perhaps it isn't being denied to them at all. Thus far, the only specifications from Bioware are that this $10 DLC unlocks the character as a squadmate, as well as unlocking a special bonus mission that goes with him. Bioware has NOT said that the character will not appear if you don't pay for the DLC. In fact, if previous leaks are to be believed (which is arguable, but it's all there is to go on), the character will still be present in the game for all players, complete with his interactions and everything. All we know for certain is that the DLC makes him available as a squadmate, and grants access to a special mission. To assert that we "know" that the DLC was in development during the original planning of the game, only to be removed at a later date intentionally, is an outright lie. We don't "know" that. It's possible, but it's not confirmed by any means. You simply THINK that's what happened, that doesn't make it fact. There is most certainly a difference.