You haven't been, perhaps, to the Philadephia Folk Festival. It's big, and been there for a long time. We have a wide assortment of others, including Bluegrass Festivals(which can be a lot like stock car races)and blues festivals--

A lot of festivals(like the Smithsonian Folklife Festival) are free, and run with support and cooperation of a variety of public and private institutions(the Smithonian cooperates with a number of related regional festivals)--some are great, some, well--

However, my bias runs toward community festivals, at churches, for instance, where music is a part of the tradition of that particular community--where, say, the band plays the participants know from their own culture, dances that they have always done, traditional food etc.

My feeling is that syncretic "festivals" tend toward becoming just another roadside attraction--special events that take on a life of their own, a lot like water parks-