Why would anyone join a “high-cost” church when plenty of “low-cost” alternatives are available? That is, why would someone join a church that requires them to spend 15-20 hours per week at church, limit who you can befriend and marry, prohibits you from drinking coffee or beer, and bars you from some forms of secular entertainment (e.g., Halloween)? This is the puzzle that the economist Larry Iannaccone sought to solve in his oft-cited article, "Why Strict Churches Are Strong." Iannaccone's answer was that strictness increases church strength in that it raises overall levels of commitment by screening out the partially committed, which increases the average rate of participation, and consequently, raises the overall benefits of belonging.
Larry's sometime collaborator, Rod Stark, drew on this insight in his Pulitzer Prize nominated book, The Rise of Christianity. He notes that the early Church placed heavy demands on members, to the point of being willing to die for their faith (i.e., martyr). And while the martyrdom of Christians was sporadic and relatively minimal, people who joined the early Church were expected to fully participate in its ministries and worship, which in turn generated many "this-worldly" rewards to church members (p. 188):
Because the church asked much of its members, it was thereby possessed of the resources to give much. For example, because Christians were expected to aid the less fortunate, many of them received such aid, and all could feel greater security against bad times. Because they were asked to nurse the sick and dying, many of them received such nursing. Because they were asked to love others, they in turn were loved. And if Christians were required to observe a far more restrictive moral code than that observed by pagans, Christians – especially women – enjoyed a far more secure family life.”
Thus, although membership in the early Christian Church was costly (e.g., martyrdom and other forms of sacrifice), it was still a bargain.
Iannaccone's theory has been applied to a number of different settings, including secular ones (e.g., the environmental movement). It is also the subject of the most recent Research on Religion podcast ("Larry Iannaccone on Sacrifice, Stigma, and the Economics of Religion"), which I highly recommend. It is available at iTunes and at the Research on Religion website. I also provide a more in-depth discussion of this theory at: "Why Evangelical Churches Thrive (or, Why Strict Churches Are Strong)"