It’s unfortunate that your bosses think that way. But the key to getting them to open their eyes is to talk to them about what matters to them - money. You need to show them that a proper development system will save them money in the long term. This could be by documenting the lost hours debugging the production system that could have been avoided with testing on dev, or the time rebuilding your prod system after a screw up. And potentially positioning the dev system as a fallback for your prod system, thus eliminating risk of downtime.
So rather than saying you need a dev environment, you need to show why you need a dev environment, and how not having one is hurting your company.
Here are some questions that other people have asked about similar concepts:
Should I propose a big change as a newcomer?
How do I approach my new boss in my new job about major changes in my working environment?
How to deal with a boss who has lost touch with modern software development?