It's raining like hell here, but i know the owner of the Driebergen track, so i'll go ask for the prices for about 15-20 people for 2 hours or so.. i'll do that tomorrow, as i have lots of free time then.
Atleast i know it's not expensive.. Oh btw, the "slow" karts have GX180 engines, so yes 180cc, and the fast karts have the same GX180 blocks, but delimited (i could delimit them as i worked there as a track aid manager and stuff lol, it's one red plug to pull on the engine ^_^ )
the REALLY fast karts are the 6 karts that very few people even here know of, those six all have twin 180cc blocks xD
My dad converted those karts from the standard about 8 years ago and they're fast as hell when handled properly.. those things are expensive to drive (the engines aren't stock so they use LOTS of fuel lol) and mostly private though.. but i'd stick to the single-engine karts here, fast enough
you can't get to the top speed on those here either when delimited physically, and then you're already doing about 95 km/h @ 9750 RPM so yeah..
Anyway, as i said i'll report some estimates tomorrow!