Adjusting for exchange, $1.10 is roughly what a 2x4, steel or wood cost me.
Your project looks great. I added a 'U' channel in my studs because it stiffened the studs and makes everything stronger.
As for attaching trim, etc, there are two ways: you could use trim screws, which have heads the size of thos of fat finishing nails, or run a (eg) 3" strip of 1/2" plywood along the bottom instead of drywall. The pros use the screws.