This is a good article - and certainly timely. The issue is complicated because our society seems to accept a few artificial mechanisms on top of the necessities of commerce. The simplest definition of economics is the allocation of finite resources, and money is just one of the most efficient means of exchange. Beyond that, though, we have to look at what sorts of artificial constraints there are which specifically affect campaigns and advertising in general.
One of the biggest issues here is that the broadcast media are run by artificial monopolies granted by the FCC. Before the FCC, anyone could put up a radio antenna, and since there's always a limited range this would not result in as much chaos as you might think. Instead, the FCC makes it illegal for anyone to broadcast radio or television without specific permission from the government. The result of this artificial restriction is that a few corporations are the only ones who can manage to obtain the permission, thus creating an artificial monopoly over the airwaves. My point is that the biggest reason that airtime is expensive is that it is artificially limited by the existence of the FCC and its restrictions on legal access.
In contrast, one is still able to run a campaign by walking door to door, signing up volunteers to get the word out, using the limited public access on cable networks, putting up a web site or even just a video on YouTube. As a side note, I suggest that the only reason that the internet is still a viable media for the general public is that it is largely unregulated. I predict that Network Neutrality legislation would start the process of turning the internet over to purely corporate interests - which is ironic, since the whole topic is based purely on the fear that it might happen. These side-issues are important because, as you note, the internet offers some of the best opportunities for inexpensive advertising that has not yet been so thoroughly monopolized as a result of government restrictions.
Another huge issue besides the government manipulation of the broadcast market is our fiat currency. The dollar is weak purely because it is not based on anything solid, and because legal tender laws do not allow U.S. citizens any other choice. The Fed is printing dollars like toilet paper, and they've doubled the money supply in a very short time. Even without the issues of limited airtime, limited broadcast frequencies, and all of the other natural limitations inherent in a resource like radio media, you raise a good point by mentioning that the falling dollar makes these problems even worse.
The strange thing about the topic is that campaign finances are not really the limiting factor keeping independent and third-party candidates off the ballots. The unfortunate truth is that most states have laws which make it impossible for anyone to run for office without joining the two-party system - a system which is clearly corrupt and lacking in any examples of staying true to their founding principles. Instead of allowing these real barriers to come to light, the establishment makes a big noise about the amount of money spent, without admitting that each party got $16 million from the government to run their national campaigns, or that outsiders are completely excluded. Campaign finance is almost completely a red herring.
To get back to your point, advertising costs are indeed likely to go up. There are many reasons for this. Unfortunately, these and other factors contribute to a system which is not the best for business. Hopefully, we can reign in the bad practices of our representative government instead of making the problem even worse.