If you have to market the whole thing on your own and find your own audience, what value are they providing? Hosting the infrastructure? Fine, let me pay a per download price or a monthly hosting fee. Or better yet, let me host it on my own infrastructure.
Verifying the security of the app? The customers should be paying for that, not the developers.
That's the issue here. They want you to pay a ransom but they don't actually provide any value for that ransom.