http://www.quora.com/Coworking/Whats-the-best-way-of-providing-coffee-in-my-new-coworking-space/answer/Alex-Hillman?srid=xym&st=ns
We've since added a new Chemex pourover, and an espresso machine that gets daily use, but not a lot.
But as I mention in my Quora post, it's the beans that are worth spending the money on. Almost daily we get comments about how great our coffee is, even the stuff that just comes out of the commercial drip setup. It comes down to 1) a decent water filter + 2) the best local, fresh roasted beans you can buy, ground to use. We picked up a commercial coffee grinder like the ones you see in a grocery store last year after killing a bunch of consumer burr grinders and it's been awesome.
But back to your question about budgeting for coffee, we spent $5600 in 2012 on beans and related supplies, up from $3500 in 2011. That's $110/week on average. I hesitate to crunch that number down to the individual day or even person, because it would not be representative of anything worth making decisions based upon.
But I'd also urge you to rethink your strategy about comparing your membership costs to cups of coffee at Starbucks. You're selling something that Starbucks can't offer (and I'm not talking about the space), so price fixing against them (and worse, below them) for the sake of marketing sounds like a decision that you'll regret before long.
Think about the value you're offering. It should be a LOT more than the coffee. Why price yourself below coffee costs?
Furthermore, anyone drinking 10 cups of coffee in a day is likely to be a short term member, given the likelihood that their heart explodes from over-caffeination ;)
Bottom line takeaways:
1) Buy the best coffee you can afford. Buy fresh, local beans. Grind every pot fresh. Your members will thank you, and tell their friends.
2) Price on value, not on your "competition". Starbucks probably isn't your competition.