I seem to remember when I lived in Texas that a license to own one of those was about $400.00 a year.
$200 for a lifetime in any state (per weapon) for full auto
I think the Lahti is semi auto but falls in the category of “destructive device”
I think the tax stamp is the same, but I am not certain.
You used to be able to buy those via the mail from the back of magazines with ammo for like $265 bucks.
Now the ammo is like $20 a round.
Somehow no one was ever killed with one in peacetime and the world was just fine.