The "fully funded" talk is somewhat accurate. Yes, those within some DAs do not have to pay. The "fully funded" part comes from their affiliates. As an example, FC Dallas has a "fully funded" DA, but they bring in around $15m from their affiliate clubs spread throughout.
Sporting KC likes to talk about how they do not support the pay-to-play:
But, they have no issues in charging $340 for a fall "Center of Excellence" program, $180 for winter, and another $340 for spring ($860 total). Then, they also have no issues with their affiliates running pay-to-play structures. There are 12 SKC affiliates spread from Nebraska, Iowa, Kansas, Missouri, Arkansas, and Indiana.
These aren't the only guilty parties. Chicago Fire have an affiliate in Louisiana. Colorado Rapids and Seattle Sounders have affiliates in North Carolina. Sure, they can call their DAs "fully funded," but what they mean is the funds are fully paid from other participants who never have the chance to truly join our DA.
At least Minnesota United and DC United are honest enough to charge their DA participants. They've been honest about it saying that a fee keeps "skin in the game" (essentially).