My first-order assumption is mostly inline with yours, Second Chances. That is, that the real money value of Stars should be relatively fixed, and the value of items in the StarMart (good working name) remaining pretty constant. I do expect, over time, as real money inflates, those inflationary pressures will force us to raise the price-per-Star in real money, but that should happen in line with how our costs rise (and how good is our ability to offset rising costs with more volume rather than by raising prices).
There might be tweaking of StarMart items' pricings as we decide to put things on sale, or we decide older items should be less expensive. I am a big fan of auctions to help us gauge pricing of some things. If we do things like "costume packs" and the like, where there's an element of randomness to what you get for your Stars, I expect the AH-value in Stars (and in-game currency) for certain items available in those to fluctuate based on their rarity and popularity. We could do some behind-the-scenes tweaking of effective Stars-pricing of those items by adjusting their rarity in random-packs.
I would dearly love to use Stars as the medium for paying for subscriptions. One concept I really liked that I read in my research into others' approaches to modern-day games and monetization is that of the "microsubscription." As I conceive it, this amounts to examining each aspect of a subscription (including the possible "tiers" for different-priced subscriptions) and breaking it down to individual perks. You then let the players "build their own subscription" out of those micro-subscription items. For ease-of-use, I would definitely want a "standard package" of subscription options (basically, what you'd get for the "standard" subscription fee, but leaving out the "premium subscription" services), but selecting that is just getting an easy package. You can customize it by taking out things you don't want and adding in things you do.
The drawback to using Stars for subscriptions is that it means the idea of a "stipend" of Stars to spend as part of the subscription doesn't make a whole lot of sense. "I spend *150/month (if a Star is worth $.10 each, roughly, that'd come out to $15/month), and I get *50 to spend each month in a stipend" will have people eventually engaging in the fridge logic of, "Well, why don't they just charge *50 fewer for the subscription?"
I believe microsubscriptions help answer this question. We empower the players who wish to pay a subscription fee to set up a dollar amount per month, per six months, or per year, and give increasing flat stipends of Stars per month to them. The subscription tool will tell them how many Stars/month they need in order to have the package they choose to put together out of the microsubscriptions. If they want a stipend of Stars for incidentals, they can make sure they have enough. If they want their microsubscriptions "paid for" by their real money subscription, they are; it just comes out of their stipend for which they've paid.
I'm also toying with some ideas for how to make some in-game currency-sinks that will scale better with the amount of wealth a given PC has, making it harder to hold on to increasing amounts of currency while making the sinking of it an enjoyable experience. The massive currency rewards high-level PCs get will not feel like ho-hum amounts that just contribute to inflation if we can pull it off right.
This may or may not serve to provide sufficient safety valve for currency-to-Stars rates on the AH. We will need to see how this goes, because ultimately there's only so much we can predict before we see how it works. We do welcome ideas and suggestions if anybody has them. I think part of it will be that we're not just having currency-for-Stars on the AH; players can put items up for currency, stars, or even post it with minimum prices in both and some mechanism for determining whether the high bidder was in Stars or currency (if both prices were exceeded). Effectively, sell whatever you want to sell on the AH, and sell it for currency or Stars. (Currency will only sell for Stars and vice-versa, for the obvious reason that selling them for themselves is silly and can only lead to people accidentally screwing themselves. But either can buy other items and other items can sell for either.)