Nvidia has a monthly subscription costs if you don't want the free plan limitations like a queue time and a one hour session limit. Stadia's free plan limitation is only 1080p and stereo instead of 4K resolution, 5.1 surround sound, and HDR.

If you're just buying a single game, Stadia comes out ahead on price when you're only paying $60 for the game rather than Geforce Now where you pay $60 for the game and then a monthly fee for every month you're playing.