Donald -
I assume you are driving this question and if so you're going the wrong way.
1) The answer is not on this forum. This forum is full of die hard veterans. They are not your market.
2) You seem be to trying to monetize the product based on current audience. That's the wrong approach. The audience for online games is much different than the audience for board games.
3) You want market share. It's really the only thing that matters. The only real win for you here is to get a lot of buzz. You want to reach well beyond your current audience. Tapping your current audience a second time is pretty limited.
4) A high pricing model will NOT generate buzz. What's much more likely is that if you come up with something complicated or expensive you will not get enough numbers (remember, isotropic is 'thin' for game matching and it's free). Dominion is more about playing an opponent than something like Angry Birds. Beating the mediocre AI is going to get dull quickly. Having no one to play on the server makes this an instant dud.
5) Your real win scenario is having bloggers and other writers say stuff like - 'I found this really cool new game, blah blah Dominion blah blah, and it's $X at the ITunes store.' You aren't going to get that by charging $10 a set or some other crazy number.
6) Market share allows you to do everything. Lack of market share means you do nothing. Remember how you couldn't get a game published and then there was dominion and now you can publish just about anything you like? Well the same thing applies to online. You need a hit.
7) Based on all of the above you need a really simple, really cheap model. You want market share. Nothing else matters. Charge something outrageously low, like $1 a set (a full set) or $5 for everything. Why? Because anyone will shell out $1. And what you want is scale and volume. You need people to give it a try. The base set for free is the right idea but I don't think its enough. Giving people a fraction of the experience is going to stink. Dominion is a simple game. Anyone can pick it up. Give them the chance. Yes you have server costs. How much can that possibly be? Bandwidth should be zero. What you need is for that girl on at the coffee shop to tell her friend to just get the app so they can play and then have her tell her friend and well, you know.
Scale. Volume. Market Share. That means stay cheap. And asking people the most they would pay is 100% the wrong direction.
I don't buy this on desktop, where it's unlikely to get more players than isotropic (since isotropic is free). There are currently ~7500 players on the isotropic leaderboard. Sell the whole thing for $5 each to these people, and you still have something like a mere $50,000 as your total revenue, oops.
Now, in the App Store (for iPad), there is an opportunity to get a lot more volume, so maybe it makes sense to reduce the prices there. I feel this discussion has been mostly about the desktop version, though, since that's what isotropic players will care most about.