If it is relatively easy for non-members to gain free access to the
space, programming, and resources, isn't the "value" members receive is
quite low. If, however, you only allow members access to some of those
things, the value is obviously much higher.
Decreasing the "per member" share of shared expenses would seem to
diminish the "value" provided. So: (i) increase non-membership incomes
(so donations, rather than dues are paying for many hard-to-value
items), (ii) increase total income (more members? more
goods/services/programming for which you charge?), or (iii) decrease
operating expenses.
Most other hackerspaces say either "taxes are hard. consult a tax
specialist" (e.g. noisebridge and hacker dojo) or "dues are not
deductible (e.g. AMT). The latter seems overly conservative, but the
former doesn't communicate with members the benefits they are entitled to.
Form 990 (think 1040 for 501(c)(3)s) has a line for the benefits paid to
or for members. So, all 501(c)(3)s have to do that hard job of defining
these values anyway. Surely they don't just say that is equal to the
dues times the number of members?
--Rick