I'm pretty sure that's an error somewhere. We stayed in June for 4 nights at Ling Bao and it was around the £350pp mark. Phantasialand itself I found to be reasonably priced, if you stay clear of the bottled water and soft drinks then you should be okay as they're extortionate for some reason.
We were a bit impatient when we got there and decided on a taxi from Cologne to Phantasialand which was expensive. On the way back we found it was very easy by public transport and very cheap. Train from airport to Cologne, change (take in some sights if you can) then a train from Cologne to Bruhl, there's a shuttle service from Bruhl station to the park, we didn't pay for it when we were there, I'm not sure if it's free all the time.
If you're wanting to cut down on budget by buying your own drinks/alcohol then buy them before you get to Phantasialand because once there you're very much out of the way for anything, 2 of my friends went on a 'beer run' and returned over an hour later after walking a fair few miles to a shop lol