None of the next is considered an ad, just an idea comparison. QCFDesign still rules!
At the Flash games of Artix Entertainment (mostly known from Adventure Quest), each time they release a new game (with free and paid version), they give players a chance to become "Founders". A Founder is someone that becomes a paid member within 1 month of the release day.
It will give you something special, unobtainable once the first month has passed. It may include (depending on the game) something simple as a special badge at the character selection screen, a noncombat pet, a donation to Child's Play Charity, a warm and fuzzy feeling of helping the game developers, etc...
I myself am Founder of their game AQWorlds, and therefore I obtain a Platinum baby Dragon. It's a little noncombat pet I'm proud of to have and to show off to everyone in multiplayer.
In the games Artix Entertainment develops, there are also holiday events, like Halloween and Easter. In those events, you can also obtain other noncombat pets (e.g. a walking pumpkin at Halloween), only available in that specific event. After that event ends, it can't be obtained any more. The people that have obtained the said walking pumpkin can be proud of their pet. And while they can't obtain a Platinum baby Dragon anymore, if I didn't do the Halloween event, they can be proud of their unique pet while I can be proud at mine; yet having nothing extra in quantity of pets.
Do you get what I mean?
You can have the premium members/special edition buyers something special, unobtainable by any other means, yet not that special so you can add special items in later of the game other people can be proud of to have and the premium/special edition members don't necessary have.
With an additional class, it's difficult to keep players happy. If it's an overpowered class, it's a dead giveaway players want to play the class, even if they first bought the normal game and later suddenly realized they want to play the class but don't want to buy the game again with the price doubled (which they already have once). (So if they pay 15 dollars for the normal game, then wanting the extra class and paying an additional 30 dollars instead of the price difference between the two: a total of 45 dollars for the game (two licenses but they only need one) plus the additional class.)
If the class is underpowered (e.g. no special abilities, aka. the "No"-class), hardcore veterans which don't had the money for paying the game at first yet still wanting to play that "neutral" class to see if they can win, even without automated passive abilities, ... same thing.
(I for example can't call myself hardcore, yet I still love the game a lot, paid the premium package with PayPal. A few months ago, I sent 40 euros to my PayPal account, and at times, I bought cheap 5-dollar games on Steam, making my budget lower slowly but steadily. Now my budget was around 20 euros, then I saw Desktop Dungeons pre-order. Insta-buy, since I want to help support the dev's of the game. I bought the 15 dollar edition, making my PayPal budget lower to around 5 euros, and remembering myself to re-fill my PayPal account one of these days.
But it could also be I had only 10 euros left and couldn't buy the special edition. Just saying that hardcore supporter is not the same as having the money or ability to buy the special edition, even if they love you that much.)
Ps.: The 75-dollars edition, is part of that money gain for the travel to the E3 or am I wrong?