Option for only 1 customer to book but multiple inventory

[Valentina R]

Add-ons cannot be used in this case, because the staff with custom pricing is used which doesn’t calculate well with add-ons. So, inventory has to be used so that one customer can select from 13 to 30 people for a trip. But only one customer can make the order.

Is there a code snippet one can use?

Requested here. Was asked before.