One can imagine a number of different ways for the public to fund drug development, and one of those is the current patent system. The idea is that by granting companies temporary monopolies which they can exploit to make money, the company's incentive to create profit will as a side-effect produce a public benefit (the availability of new drugs that save people's lives, etc.).
For this to be an effective/efficient solution, we want the drug company's incentives to line up *well* with the public good. But it isn't at all clear that they do. Some of the arguments being cited here are evidence that they don't.
For example: The massive marketing budgets are presumably paid for by increased profits from people buying the drug in question as a result of the marketing -- but those new sales are probably mostly from people who otherwise would have been happy with a generic, or nothing at all. So we could say oh well, sucks for the people who end up paying too much; they should have been smarter. But first, it strikes me as horribly immoral to expect every member of the public to be more educated about the state of the art in medical care than the professionals who are trying to fool them into spending too much. And secondly, since health care costs are spread out over everyone (by insurance premiums, by prices set on the assumption that assume some people won't pay, by public health coverage), those people who pay too much are hurting everyone. (Indeed, part of that marketing budget now goes to these clever rebate schemes for new drugs, whose whole purpose is to re-create the "moral hazard" that American insurance companies try to avoid by having higher co-pays on brand name drugs versus generics. The result is that my wife's *brand name* drugs are *cheaper* -- for us, out of pocket -- than generics would be. But the insurance company is still paying full price and getting screwed, which eventually comes out in everyone's premiums.) So here the patent-based develop-drugs-to-make-money system doesn't serve the public interest.
Basically the same thing is happening every time the drug companies do some profit-driven horrible thing (denying drug availability to dying poor people, declining to research important but less profitable conditions -- malaria was mentioned, and apparently in the UK the drug companies have just said eh, screw it, and fired all their neuroscience researchers, etc., etc.).
So while profit-driven free-market enterprise is a very efficient way to get certain things done, it's far from clear that it's actually the best way to develop drugs. Other systems -- like, say, taking the same amount of money from taxes and giving it to non-profit research institutions -- obviously would have their own problems, but not these ones, and these ones are pretty horrible.