In my group, people buy whatever they buy. If they don't have a PHB, someone else will lend them one. If they don't have miniatures, someone else will lend them one.
We kind of expect you to get dice eventually, just because those are more personal.
As far as power cards go, we've just been putting the powers directly on the character sheets (they usually end up being typed and printed). That's an "extra," so chances are everyone will get their own if they want them, and not bother if they don't. If someone has a set they're not using, I'm sure they'll share, but I don't anticipate that.