It depends on their pricing model. It could probably be one of the following:
Purchase from Game Store & run.
Hybrid of the above two.
Out of those, subscription-based model sounds like a win-win for both Google and it’s consumers. We can expect it to be priced around 15–20$/month where the players will gain access to a wide-range of titles. This option is most likely to be in place given that Google wants to be the ‘Netflix for Gaming’ ! It could also charge per hours of usage (which sounds good for new-entrants) and could have a free access-period based on credits. Again, this is just speculation and the numbers could go high or low.
If Google is really dead-serious on Stadia’s adoption, we can expect the price to stick to the speculated range or maybe even less- especially since Amazon, Walmart(yes, you heard it right, WALMART!), Nvidia, Microsoft & others are all in the race !
Not to be carried away by the fad, the second option & third option could definitely stick around for some-time until people are comfortable with the notion of ‘Cloud gaming’ itself. A lot of hardcore gamers would want to mod the game, own a copy of it & for them , the notion of just ‘paying for access’ could be a huge turn-off.
However, considering the benefits and hoping that Google will stick to its plan for real, we can see better pricing models. It’s also worth remembering what Netflix did to Blockbuster