At least in Silicon Valley there are several causes: local governments and/or quasi-govt. agencies (such as fire departments) want to levy "permit" fees on organized events taking place in their jurisdiction where in earlier years they didn't, to the extent that many events now need effectively a lawyer to negotiate with these various agencies; county health departments want all food/beverages served to adhere to restaurant-level food-prep, storage and serving standards, preventing events from relying on volunteers to prep and serve food and instead forcing them to use professional catering or costlier pre-packaged food; there may also be insurance premium costs increases to factor in; and, not least, everyone looks at what everyone else is doing and says "Hey, so-and-so's event is charging this much, so we should be able to charge a similar amount too".