In your experience, how much $$$ are we talking about ?
It all depends on the scale. Renting a small nightclub can be pretty cheap, a lot of them will let you throw your event for free if you'll bring them more people then they usually get. If we want to go bigger, we have to think a few thousand dollars location. I would definitely rent a location that already has a sound system, lights, sound tech, etc. You save a lot of money this way as rental is one of the expensive things. The next thing we have to consider is the artists themselves. This is where contacts come in. As this is a fundraiser, a lot of bands who believe in the cause might play for very cheap, or even for free.
Bottom line is, give me 2000$ and a team of volunteers, you'll get a small, local show. Not that big and the only reason it would make the news is because of the pirate party association. We could probably have one popular local band. At the same time, 10 000$ can get us a much bigger show. Keep in mind that the outrageous amounts we hear about on the news usually involve superstars asking for ridiculous amounts. I definitely think the option is doable, and I would propose forming a committee to organize the event. We can look at an area, discuss the potential there and decide on a scale and budget accordingly.
The problem arises with the expenses vs revenue balance of a concert. You have to be certain that you'll make back the money spent on Venue, Liscenses, Food, Beverages, Insurance, Entertainment, Advertising, Collateral, Product Manufacturing, Staff (including the organizer), etc. An immediate rebound is that advertising can be done solely online to reduce costs, but then you end up with 5 attendees (happened last summer in Ottawa). It's also about an 8 - 12 month planning period for a decent concert.
I've seen things like that happen. Generating hype for an event can be hard, especially if you're unknown as a promoter. The whole debate about using flyers vs promoting online has been raging for years. My opinion on it is that promoting only online will work if you already have people interested in what you do. Sure, flyers are expensive, but if used properly, they work. As for individual expenses, it's possible to save money on most of those and they're really a case by case thing. Usually a lot of them come with the venue.
Oh, and here are some of my best events, so you get an idea of what I've done in the past and know I can at least pretend I know what I'm talking about.
http://www.rave.ca/en/event/raves_r_us_2/ Raves'r'us 2, probably the best party I've thrown. About 400 people, huge turnout for the Montreal rave scene at the time.
http://www.rave.ca/en/event/time_machine_2_frankie_bones/ Time Machine 2, this one was aimed at a slightly older crowd, as I brought in "oldschool" djs, including Frankie Bones headlining the event. (for those of you who don't know, he's pretty much the one guy who brought raves to north america.) 250-300 ish people showed up.
http://www.rave.ca/en/event/project_mayhem_explosive_kandyfest/ Explosive Kandyfest, last party I threw before my retirement. About 300 people if I remember correctly.