I don't disagree with you that games cost money to make, Dom. That's kind of obvious. As is the suggestion that you or I or anyone should be happy to pay a relatively stable price for a quality game which can then be augmented by downloadable content. This is a fair model, and works to the benefit of the developer as well.
As Todd Howard of Bethesda told me, they use the down time between release of one game and development of the base technology for another to accumulate art and story assets which can be released as downloadables. This keeps the revenue flowing in and prevents them from having to lay off and then re-hire portions of their staff, as other developers do. So I see the benefits quite clearly. And in some cases, I approve.
Hell, I buy downloadables. It is not the general theory about which I disapprove. It is, as I've clearly stated, this example of GTHD and the potential it suggests for even more egregious future abuse. A "base game" as you say, Dom, is one thing. A menu with no cars and no tracks is another. Episodic content models take this a bit further by resurrecting the shareware system and offering small chunks of game for relatively small amounts. So far it's working, but as with microtransactions the potential for abuse is very real and should not be taken lightly. Greed, after all, works, but only in one direction.
Are microtransactions a good thing? Yes and no. Like any tool it depends on who is using it and how. I think there are good things to come from the development of the digital distribution/microtransaction model, but there are also very very bad things. Shipping a game with zero content is a bad thing. As was offering a set of horse armor for too high a price. If no one had spoken out about that one, however, how much higher do you think they'd have gone with the bigger content? I for one am glad we never found out.