What are /r/MysteriousPackageCo's favorite Products & Services?

From 3.5 billion Reddit comments

Well, the Curios and Conundrums subscription for MPC is $30/quarter, which is under $50.

There's also Hunt a Killer which costs $30/month. It's a monthly subscription where you are trying to solve murder mysteries.

If you're looking for a cheap one-off there's the novel S. which has a lot of ephemera that let you piece together the overall mystery of the book. It's actually on sale on Amazon today for under $20.