The answer to the question, "how are you going to pay for this project?" is turning out to be sponsorship more and more often. If you don't know why organizations want to sponsor things, though, it's likely a long, hard road to find the sponsorship you seek.
As the number of media options continue to explode (blogs, books, conferences, tattoos, speaking engagements, film festivals, stadiums, entire websites...) it's worth thinking a little bit about why organizations buy sponsorships.
1. It might be a substitute for advertising. How many people see it? How much does it cost per person? (this is the cpm, but instead of cost per thousand page views or magazine readers, it's cost per thousand impressions, which come in a myriad of ways). I think this is the film festival/book fair model. It's a reasonable way to reach a hard to reach, high value group.
2. It might be a bragging rights thing. This means that the sponsor isn't focused on tonnage, but instead wants the affiliation that they can mention to others. Sort of a reverse endorsement. The thing being sponsored isn't a media outlet, then, but a license by affiliation. An example of this might be sponsoring a speaker coming to town. Clearly, the 500 people in the audience don't constitute a useful CPM, but the fact that you did it gains you authority with those that notice what you did.
3. It might be a chance to influence the organization being sponsored. This would explain why big corporations are willing to sponsor political conventions.
4. It might be a useful way to inspire and focus your internal organization. When the people who work for you see you sponsoring a worthy charity or a thoughtful opinion leader, it changes how they do their job or how they focus their efforts.
5. It makes the CEO happy and earns the organization a seat at certain sorts of tables. I think this is the model for sponsoring a sports stadium, an act that has never been shown to have any value at all as a mass media choice.
Because there are so many ways to come at this, valuing a sponsorship is difficult indeed. If you're a bank sponsoring a bike sharing service, how do you compare that to five-hundred full page newspaper ads (about the same price over a certain period of time). Of course, you don't. You can't. Instead, you must be really clear internally about what it's for.
In general, if you're clear about which of these five things you're shooting for, most sponsorships are a screaming bargain compared to traditional media buys, particularly if you're trying to reach an elite or elusive demographic.