Sam,
Not too expert ( well not at all expert actually ! ) in fly fishing. However, I would suggest that the bulk of the cost should be in the rod and line and the least in the reel. ( The reel is really just used to hold the line and the rod used to play the fish ).
I stand to be corrected however.
You could probably make your own fly box easily enough and a net ( the small handled ones ) are pretty cheap - I will see if I can find the one I have, you are welcome to use it.