It still befuddles me, especially since it's a specific format for a horror story: A bunch of rich people pay through the nose for a once-in-a-lifetime experience, and of course it kills them (though the final girl might escape). The Menu was a recent example. Maybe to get Stockton Rushed should now mean to buy a super expensive experience or trip or thing that kills you.

A drug named Stockton Rush would be super expensive, and the most amazing trip ever, and fatally toxic.

So if you're hiring someone to chart out your trip to Everest or the Titanic or the moon or something, it's good to get your legal team to do some due diligence and make sure the company knows what its doing. (For a deeper dive, check out Behind the Bastards' two-parter on Stockton Rush. All the warning signs were there he was doing mad science and not listening to his deep-sea experts.

Also, the door that only can be opened from the outside was total early foreshadowing.