I love Halloween at Joann's but everyone should know that their full prices are ridiculous and they do mark down seasonal things pretty soon after they put them out. The website also has 15-50% coupons for the weekends that can be used in-store and sometimes stacked with the store markdowns.
I'm pretty sure they price like that because they know they're going to have it on constant 30% sale after a couple weeks of being put out. Plus stacked with other coupons, if they want to make around $20-30 per item then they need to set the base price insanely high or else the coupons will kill profit.
It's a marketing technique to get people to buy stuff because they think they're getting a deal. Not because they expect to sell stuff at that insane markup. I checked out JCPenney's Halloween section last year and it was the same sticker shock despite that being a more affordable department store.