Do you pay the extra taxes every year or only the first time when you buy it new? If you only pay the taxes once then buy a used car from German or someplace else with low car prices. At least in Sweden you can buy any used car (must not be tuned in any way) that is legal in say German and import it to Sweden. After the registration (cost 1.900 SEK) you can use it in Sweden. NOTE! Used car = older than 6 month and more than 6.000 km on the odometer.
All countries have special laws, often the argument is to protect us or in this case maybe they say that big engines (heavier cars) uses more gas... Sorry for not having an answer. /Patrik with a 3.2 litre car. ;-)
Patrik Sjoblom....1993 MB 320 CE......Bought Jan 2001. Only 16.8 mpg
Stockholm.........Silvermetallic....DEFA immobilizer/alarm + Original larm
SWEDEN............17x7.5 ET35 wheels with 215/45-17 Kumho 712 ECSTA .