From Screamscape:
"Howl-O-Scream could possibly become free for some or all annual passholders this season. The move could be a smart one, as HOS in Tampa has always kind of played second fiddle to Universal's Halloween Horror Nights. In light of rumored budget cutting to the event over the past few seasons, a move like this could bring more bodies in through the gates and increase in-park sales during the event nights.
While not part of the same company, Carowinds in Charlotte, NC made a similar switch several years ago, and made the hard-ticket SCarowinds haunt event also free for their Gold level passholders and has seen much success and bigger crowds ever since due to the park's huge annual passholder base."