I wouldn't use Firefly-not even free. To ask money for this quality of generation seems exaggerate

I think the creation of images is very far from what Midjourney is able to provide. I have tried all AI engines in Firefly, I am not able to use anything because the results are very low quality, doesn't understand concepts like DOF, particles, bokeh, etc.. anything from what I have tried for 2 hours on Firefly is less than what MJ delivered 2 years ago.. and today I was able to create the same thing, in a proper way, in a single iteration with MJ (1-3 minutes). I think you should develop this AI generation much more before asking a price for credits.