Two books a month, where one is a hardback, might be ok - would the authors of both be available for question/answer session?
A cheekier suggestion might be if the publishers were to offer a set number of hardbacks to MN bookclub members, who weren't lucky enough to get a free copy, at a (very) reduced price?
I wouldn't mind at all if ebooks were cheaper than hardbacks, but they are often the same price, unless they have been reduced in a flash one day sale on Amazon (or elsewhere).