Pump It Up – fixed fee for first 25 kids. Nominal charge per kid over 25. Two parties w/ 12 kids each costs double 1 party with 24. We had 28 or so.
At home – you have to set up and tear down twice. Takes double the time.
Legoland – smaller twin effect. Same kid cost, but assuming we don’t let the kids run amok in Legoland without us, we would have to pay to get the parents in twice.
