I.e. one full bitcoin-node on a high bundwidth server generate less than 1 TB traffic in any way, right?
Never say never 
1 TB really isn't that much when it comes to Bitcoin's blockchain, it's barely enough to sync 6 new clients. Those clients by default will of course also use other nodes, so in reality many different clients will each download a part of their blocks from your node.
Is it possible to somehow limit the speed of the node on Ubuntu-server?
Just Google "ubuntu limit network speed" and it gives you options like Wondershaper or Trickle (I haven't used any of them). Or, what I would do: manually monitor it for a while, it may not even be needed.