I know its seems high, but probably sensible,
The rules in Germany changed again in 2010 - regulations now require all passenger cars and motorbikes including vehicles from foreign countries to be fitted with winter tyres or all season tyres on all axles when conditions are wintery. So not only do they need 3mm or more, they have to have a spare set of wheels with winter tyres!
I guess thats where the vast amounts of part worns on ebay come from.