I think there's a lot in the amount of play people have to their disposal. I went to an RR day at a big tuners 18 months or so ago and they had someone from DynoJet there to check the calibrations.
Their car was first on and made a lot less than they thought/claimed it had been making, but everyone else following made perfectly realistic figures and every one I've seen on there since has been likewise.
Just goes to show you that you get whatever the operater is willing to give you.
