Unless you pay it all back, at 12 months and 1 day, that 29% interest rate comes crashing down on you like an Acme Anvil in a Roadrunner cartoon, and midwife's you into a whole new world of hurt. When you see first time haunters idly musing over whether or not to spend $10K or $20K or more on their haunt, much less some $8K on one room, then that is just a disaster waiting to happen.
Consider, if they had the money, they wouldn't need to use the credit card, yes? Well, what? Are they going to have a spare $20K lying around in 12 months and 1 day that they can use to pay that debt off in full? Are they planning on winning the lottery about that time? Did they already take out a second mortgage on their home to cover expenses, and are pretty skint as it is? What if they face a financial crisis? Based on real world results, if they didn't have it at the start of the year, they probably won't have it at the end of the year either. I know I didn't.
These are all realities that regular people face, even without taking on something as risky as a haunt. I don't know how much credit card debt you have, but I know from my own experience and the experience of millions of other people, this is a risky game to play.
(Now, that being said, a few thousand in available credit for incidentals during a successful run, that might be more tenable.)