Edit: *sigh* "Its common for full nodes on high-speed connections to use 200 gigabytes upload or more a month. Download usage is around 20 gigabytes a month, plus around an additional 100 gigabytes the first time you start your node." I guess that I will not have a full node after all

all dependant on how many connections to other nodes you have.
less connections = less bandwidth usage
And as far I understand Jonas Schnelli had done sth for limiting this upload traffic a bit, by some parameter - not sure if this is part of BU?