At no cost to the consumer, but not necessarily no cost to the publisher.
It's not clear whether Geforce Now requires enhancements to the various launchers in order to work - Ubi, Origin, Battle.net etc. If that's the case then there's certainly some cost involved.
Then there's the fact Nvidia is offering a paid service. It's likely due to pure greed but where there's cash involved everyone will want their cut. Though I'm struggling to see why publishers should be paid to allow you to play games you own on cloud hardware.