In which ways do app developers cover costs of cloud services?

In which ways do app developers cover costs of cloud services?

I have a few ideas for mobile applications, some of which could benefit
from some cloud functionality.
For example, an application might allow a user to take photographs with
their phone which would generate a list of thumbnails, imagine a to-do
list which comprises photographs rather than the traditional text entries.
With the help of the cloud, the user could sync the thumbnails on multiple
devices, or perhaps give access to the list to another person using a push
notification to their phone, allowing them to then download the
thumbnails. There may also be a cloud-based database being used.
It's a simple scenario but it raises some questions for me.
Most mobile apps are currently either free (maybe monetised with ads) or
have an initial one-off cost, yet ongoing cloud services cost money. If I
developed an app that had 1,000,000 users all storing photos in the cloud
and they use the app for the next ten years then the cloud costs could be
substantial yet income from app sales may be low after the initial influx
of users.
So how do other developers manage ongoing cloud costs?
Are most apps that make use of the cloud subscription based?
Can someone who has already done this type of thing share their experience
regarding cloud costs and app monetisation?