Complex sentence: Religion is an expression of conspicuous leisure and of conspicuous consumption, an activity of social, but not economic, consequence, because a church building is an economic waste, an unproductive use of land and resources, and the clergy are people employed in unproductive work.
Split into simpler sentences: Religion is an expression of conspicuous leisure and of conspicuous consumption, an activity of social, but not economic, consequence. Hence, a church building is an economic waste, an unproductive use of land and resources, and the clergy are people employed in unproductive work.