The german guy he's talking about is Randy Engelhard from Heaven of Colours in Zwickau, Germany. And for sure you'll have to pay an added celebrity status as Randy is a leading actor in a popular german tattoo tv reality show.
Randy estimated around 7h for the chest piece while charging 1500€. That's around 200€/h, think that's a solid price for a talented and busy artist. And as he's so busy he just proposed the possibility to do this piece on a sunday for double his usual rate to get an earlier appointment. Otherwise I would expect him to have a waiting list of at least 6-12 month, if not even more (not sure about that though...).
But I don't think it's possible to calculate with these numbers and just say: Well, a whole sleeve from this guy would be around 20k... Taking into account an hourly rate of 200 bucks I would probably expect a sleeve done by him around 20-40h and so by 4k - 8k €.