Budget for hosting a playdate.
A playdate divides into per-child costs that scale and shared costs that do not. Snacks and any venue entry are charged per head; craft and game supplies are bought once for the group. That structure explains why hosting at home is dramatically cheaper than a soft-play session — removing the venue fee removes the only line that multiplies. The cost-per-hour figure is the useful comparison against paid childcare, and it usually favours hosting by a wide margin.
Playdate hosting cost
Total = children x snacks + supplies + children x venue fee; per hour = total / hours hosting
Yes — set the venue fee to zero and the total typically falls by half or more for four children, because entry is the only line charged per head besides food. Everything else is shared.
Very little. Children largely make their own entertainment in a group, and elaborate planned activities are more often for the adults' reassurance. A modest supplies figure covering one fallback activity is usually enough.
Because it makes the comparison against paid childcare concrete. A reciprocal arrangement where parents alternate hosting is, in effect, childcare at the snack cost per hour.