To complicate this may I suggest another approach? If community integrity is the goal and differentiation from $9.95's is the unique value prop for Surly, have you considered modeling your financial goals on The Slicing Pie model?
Slicing Pie would have you take the costs you incur at a 4X valuation and your risk (that is your market value for the time it takes to do the work) at a 2X valuation and derive at the number you should aim for.
In this instance it would be $4K for the costs (because it's easier to save money than to spend it, it has a higher valuation) + whatever your market value is (for whatever job you could be doing other than this) X 2 - then divide that by the number of Users and then either try to raise that amount by a monthly fee or by donation.
This way the community integrity remains intact - you're charging a fair price and getting value at the same time - and won't have to resort to the methods which introduce variables that dilute the community integrity.
By the by, I'm all for you making money, and if that's the goal then you should charge as much as you can while maintaining a paying user base.