Actors & Film: What is a "name" worth?

From io9:

"After hearing about Hollywood's sticker shock over the Bioshock movie's rumored $160 million dollar budget, we knew they'd be coming up with new ideas to try and lower the overall cost. But if the rumored lead actor gets the part, it'll be kind of a steal for Universal. Prison Break actor Wentworth Miller took to his Twitter to let his fans know that he's talking Bioshock. And later tweets seem to imply it's indeed the video-game's movie version.

This means a few things: that Hollywood is moving forward with the long-in-development film, budget problems or not. Plus it means actors like Miller are going to be getting a second look as they are a bit cheaper than the big Hollywood A-list actors. I'm completely for this. I like Miller — he's a solid actor in Prison Break — and I'm interested to see more from him. And I want to see who else they start to tap for roles in this film."

The question that arises from this is: is a known actor needed in an already established franchise/concept?

Let's look to the most popular film adaptations: comic book movies. Recently, the titular role of Thor went to an completely unknown actor, Chris Hemsworth, whose biggest domestic role thus far was 3 minutes as James T. Kirk's father in the new "Star Trek". I couldn't be happier that a big budgeted actor didn't get the role. Or if you want to be even more detailed; Sam Worthington. This fellow is everywhere. He was first cast in James Cameron's "Avatar" as the lead. He was cast in that before "Terminator: Salvation" which was America's biggest exposure to him. He was also just recently cast in the "Clash of the Titans" remake.

All of these castings were done before any of the other films mentioned were released and were able to show his box office "draw". Let's look at the facts; James Cameron, a living legend, can cast pretty much anyone he wants to because people are doing to see what HE does, not so much the actor. Personally, I couldn't be happier to hear about Wentworth Million's possible involvement. I mean, it could have gone to one of several other actors that Fanboys (and yes, these people make or brake a movie through power of the Internet) don't care for.