1.) Price has not been announced but it will be really close to the other inventories and in the $30-40 Range
2.) 172mb with all the demo content and items
3.) I think it is easy to implement and I will be showing a video on how to merge it with the Multiplayer TopDown Kit. That will give a good example of how to implement it into your own projects.
4.) It is build very clean and very solid this makes it extremely expandable. The only limit is your willingness to learn and create.
5.) There is a video showing how to add new items and with the video that is coming soon to implement it into the MP TopDown Kit I think these show off enough of the system without giving it all away.