Found the website for the party I mentioned above.
£15.50 per child.
Plus another £4.00 for the extras (I saw a party bag, I know which option they chose).
Possibly plus food and drinks for adults, allowed in on a 1:1 basis. Although they may have been expected to shift for themselves.
The invites went out to the whole class of 30, so let's suggest 20 came.
£390 even if parents aren't catered for - $610.
Okay they have bumper cars, a climbing wall, one of the largest play frames in North London (apparently). But no pass the package