Unfortunately it isn't possible to provide a demo version as it will just contain all functionality and will work forever. Also, I am not allowed to give you a discount.
I am selling my product via Envato Marketplaces and they are the exclusive sellers of my plugin. I am simply not allowed to distribute the plugin in any other way than via Envato Marketplaces. If you would like to receive a discount for what reason, you should try to contact them.