Here the actual listings of 1998+ Audi A6 Sedans:
http://suchen.mobile.de/fahrzeuge/searchrefine.html?categories=Limousine&__lp=10- 37&scopeId=C&sortOption.sortBy=price.consumerGrossEuro&sortOption.sortOrder=ASCE- NDING&makeModelVariant1.makeId=1900&makeModelVariant1.modelId=10&makeModelVariant1.- searchInFreetext=false&makeModelVariant2.searchInFreetext=false&makeModelVariant3.- searchInFreetext=false&vehicleCategory=Car&segment=Car&minFirstRegistrationDate=- 1998-01-01&siteId=GERMANY&negativeFeatures=EXPORT&damageUnrepaired=NO_DAMAGE_UNREPAIRED- &export=NO_EXPORT&customerIdsAsString=&lang=de


Oh, I must admit, that I've expected higher prices. There are several for less than 4000 €.
When you check the 1998+ Avant-versions, too, the first and cheapest one is a RHD-car from Britain:

http://suchen.mobile.de/fahrzeuge/showDetails.html?id=112613476&__lp=1037&scopeId=- C&sortOption.sortBy=price.consumerGrossEuro&sortOption.sortOrder=ASCENDING&makeModelVariant1.- makeId=1900&makeModelVariant1.modelId=10&makeModelVariant1.searchInFreetext=fals- e&makeModelVariant2.searchInFreetext=false&makeModelVariant3.searchInFreetext=fa- lse&vehicleCategory=Car&segment=Car&minFirstRegistrationDate=1998-01-01&siteId=GERMANY&negativeFeatures=EXPORT&damageUnrepaired=NO_DAMAGE_UNREPAIRED- &export=NO_EXPORT&customerIdsAsString=&lang=de&pageNumber=1