TL;DR
MKBHD is shutting down the Panels app at the end of this month, citing issues with finding the right development team fit.
You can no longer buy collections, and you must download existing wallpapers before the app is removed.
Users will receive automatic pro-rated refunds for active subscriptions, and the app code is promised to be open-sourced after shutdown.
I’d figure people who think watching ads is entertainment which is basically what his video are would be the group to buy a wallpaper subscription. And he has a lot of subscribers so likely figured there would be enough suckers out of millions to make something that barely cost anything to make to see how many would bite.