As you said you are "new". I make come components for the Scale industry so I a little bit about the industry. Firstly all things are not equal.
Cost of production will certainly increase if the plane is all metal. More parts will be needed. Per material aluminum isn't as strong as balsa ounce per ounce. Weight will increase per plane hence larger engines will be needed. Labor cost will increase due to the increase parts list.
You are welcome to produce an all metal plane and see how it sells. Perhaps set an example for others?
The market place typically determines what's best for it.. so far after all these any years metal hasn't done that.. just my Opinion