THE COSTING OF PLUGIN WILL DEPEND ON THE FUNCTIONALITY TO BE INCORPORATED WITHIN THE PLUGIN.
You just have to give me an overall idea of what you want and how it should work and that's it. After that it's all up to me.
If you want to know the price and time cost estimation for your plugin, just leave me message with your requirement. I'll get back to you as soon as possible.
Thanks for having a look at my gig..! Cheers...!