From its opening in 1870, the Met had a mandatory admission charge one or more days a week, but that ended in 1940. In 1970 it instituted its voluntary-price system at the suggestion of an honorary trustee, an investment banker, who got the idea from church bazaars. Today few museumgoers probably think of church when digging into their pockets. But

Article source: http://www.nytimes.com/2011/06/10/arts/design/metropolitan-museum-admission-fee-debate.html