Expenses, including travel, lodging, conference fees (if applicable) and the same per diem as staff receive (if food is not supplied) are paid for Board-related activities. Other reasonable expenses are also covered, although everyone is encouraged to take advantage of cost efficiencies where possible (e.g., group taxis to the airport, using public transit where possible). [As a side note, these same rules apply to the FDC, for which there was only one woman candidate this year.]
The bigger factor may be time, for both of these roles. The FDC is mostly not that busy most of the year, but is hyperactive during the two 10-12 week periods a year when they are considering proposals (From my experience, a thorough review of the average proposal takes 10-15 hours total. Multiply that by 6-8 in April/May and 12-18 in October/November, and that is a LOT of volunteer time). Members of the Board of Trustees have stepped down in the past because of the time commitment expectations (including several full weekends a year, a retreat, attendance at Wikimania, and participation in online/teleconference meetings).