Well yes, the tax would still be imposed if one assembles the bikes within the country.

Believe me, people have tried all kinds of tricks, including getting a rusty HD from the forties or fifties from the states, or the EU and then pay the tax, which is very low for old-timers. After this they rebuild the bikes, so they become virtually new. If this is discovered by the police and the Tax administration, they are facing a very big fine.

And of course there is the well-known Danish scam to buy a Bike or car from another country and ride around with the foreign number plate. If discovered, and every year it happens, the person faces the tax and a fine which is the same as the tax. So they end up paying the tax two times, quite expensive bill, if one rides a HD Fat Boy....

One of the reasons why this system operates is the fact that there are no car or motorcycle factories on Danish soil, so the different governments wanna get their share on the excessive import.