The 1000 users is what you pay for in the license, with these numbers you probably end up with "standard" license and you can talk to Mendix about what exactly you need. Developers can use studio pro (development tool) as much as you like.
See pricing: https://www.mendix.com/pricing/
When using Mendix cloud, you are paying for Mendix cloud which means you are paying for users of the application.
You can choose to have Private cloud, in which case license key is offered to you. But I am not totally aware of how the licensing is considered.
In both case, you are not paying for the developers.