[PeterisP]

They probably paid because, as the grandparent post suggested, taking public funds from NIH imposes a requirement to publish the research results in this manner, so for the research team it's an unavoidable part of the expenses related to the grant - and so it's not the researchers' money nor their decision; NIH defined what they want and so they're paying publishers a significant portion of their funding for that.

[lapinot]

Indeed, most likely the question of paying or not wasn't even asked properly and this is just the norm.. In any case my point is that the problem of this capture from some scientific publishers is much deeper than just a problem of how publishing is setup. Its one of the many symptoms of how current research institutions are governed.