According to the article there are about 100 American Students at the University of Cologne. That should be about 1% of the students. Having 1% more students more who pay exactly as much as domestic students isn't something that concerns me as German taxpayer, even if there would be no benefit for us. If I would have a problem with our budget there would be much bigger fish to fry.
When I started at Imperial College London in 2004, about 30% of the students in my class were from China, Taiwan or similar. Many wanted to work in the US, some had applied to US universities. By the time we graduated, after having lived here and with the US tightening its immigration policies, most took jobs in the UK.
That was with £17,000+/year fees (for non-EU students), so they were super-rich and also clever. If studying at Cologne is free for them, and in English, that will attract potential students away from Britain.
I paid about £1000 year, like all British students, but I'd definitely consider Germany if I was 17 now. Fees for British students have increased to ~£9000/year! My workplace has a very international staff, all bilingual staff's teenage children are pretty much guaranteed to study elsewhere in the EU, with others considering it.
The University of Cologne has a rather high number of students that are only enrolled there for the Semesterticket (public transportation ticket valid in most of North-Rhine Westfalia) and as such, the official number is slightly below 50000 students if I recall correctly.
Compared to that, the 100 students are just 0,2%. The number of "active" students is around 20k I think - so the ratio is still significantly below 1%
To be fair, it's impossible to get anything close to resembling the NRW Ticket (flat fee for unlimited use of regional public transit in all of North-Rhine Westphalia) as a non-student.
The closest equivalents are either offered by the local public transit unions (which are limited to the region covered by that public transit union, of which there are a ton in NRW) or the BahnCard 100 (which covers all of Germany -- but not necessarily all local public transit -- and is ridiculously expensive).
