The people who put down that kind of money for the game put it down because they support it and they want thia game o succeed. You say it looks like a cash grab, but Caspian (Jeromy Walsh) funded plenty of it's initial development and he and his co-founder Eddie Smith have staked a lot in it. All the folks at SBS have their own livelihoods to support and it's been because of the continued support of their backers that they've been able to grow and thrive over course of the past year. Caspian and his team have been practically transparent when it comes to their approach to the game and it's development, as far as I can see, they don't intend to cut anything they've promised and haven't promised us anything on which they may not be able to deliver.
In terms of the store, they've given adequate information on the intended purposes and uses of the rewards that come with each tier, and most of them are pretty clear.
SBS is providing limited access (as far as I can gather) to higher backers because they want to provide the general community with a finished product, not a buggy testing phase. People backing are quite clearly showing that they want to be involved and help the game succeed (for the most part) and that will show in the Alphas and Betas
Anyone who's done their fair bit of research towards the game understands what the exposition phase is and what the EP store will be for.
If they took the time to explain every item in detail, things would be over-complicated at best. We don't need to know everything at this point, the general info they've given us is more than enough to satisfy at the moment.