Thanks for your response, and I'm sorry for the confusion here. If I understand what you're saying correctly, it sounds like you want a configuration where your students pay for their own hours used, is that correct?
If I have that right, this is on our roadmap, but we don't currently offer that out of the box today with RStudio Cloud spaces. At present, all project hours accumulated in a space are the responsibility of the account that owns the space (i.e. yours). We do have a couple of options that might get you close to this, but they have various tradeoffs:
The first option is the one I linked to above, where you can use a space as a "jumping off" point and have your students copy projects you share there and then move their projects to their own spaces in order to do work (you can also move their projects). Once the projects are out of your space, any hours they accumulate will no longer be your responsibility. Unfortunately, it also means you won't be able to access them until they are moved back.
The second option is to create projects in Your Workspace and change their access to public. This is different from creating projects in a space you created -- all public projects created in Your Workspace can be accessed by anyone with the link (not just students in your space), and opening them will not charge hours to you.
Unfortunately, I don't think either of these options is quite as simple as what you're after.
Why does 1 hour of actual use equal 10 hours of use.
I'm sorry my example was confusing there -- my point was that how your projects are configured can really affect how they consume project hours. Projects are configured to use a 1 GB of RAM and 1 CPU by default. In the default configuration, 1 project hour = 1 hour of "wall clock" time. If you had bumped your projects up to max RAM though, they'd go through your project hours a lot faster because they would be using significantly more resources while they run. (After I responded yesterday I did a bit of digging on our side -- it doesn't look like this is the case for you.)
Anyway, I wanted to respond here since I think a lot of this information is relevant for other folks too, and we'll also be responding to your support ticket shortly over on that channel. Thanks for your patience with this -- we want RStudio Cloud to be easy for you to use too, and I hope we're able to get something to work for you.