Estimate the cost of hosting a sleepover.
Hosting a sleepover is mostly a catering exercise. Two meals per guest plus a shared snack budget make up the bulk, and both scale directly with the guest list — which is why the per-guest figure is the number to look at before agreeing to an extra invitation. The activity and sundries block behaves differently: bedding, spare toothbrushes and a film rental cost roughly the same whether five children come or seven, so they dilute as the party grows.
Sleepover hosting cost
Total = guests x food per guest + snacks + activity + bedding and sundries
Snacks and drinks. Children graze continuously at a sleepover, and a shared snack budget set for a normal evening at home will not survive it. Budget it as a lump sum rather than per head.
Sleeping bags and mats are cheaper than duvet sets and get reused across every sleepover, so the initial outlay amortises quickly. Enter the full cost the first time and a much smaller sundries figure afterwards.
It falls, because the activity and sundries block is fixed. Doubling the guest list roughly doubles food but not entertainment, so the per-guest figure drops noticeably.