Stuart Grey wrote:
I was looking at the design of the Murphy Moose:

http://www.murphyair.com/

They put the cost at about 100k$, cheap compared to the two Cessna's and
the Bush Hawk to which Murphy compares the Moose:

http://www.murphyair.com/Product_Info/Super/compare.htm

From their engine page, half of that cost is probably engine.

Empty weight is 1450 pounds.

At Boeing surplus, a sheet of aluminum runs about $1.64/pound (Not
including the Boeing discount). At 1450 pounds, that's only about $2400
worth of aluminum. The rest is labor (they half build the airplane),
mark up, insurance, support and so on. A really cheap guy who doesn't
have a lot of money, such as myself (who some say don't deserve to fly,
and maybe so...) might be tempted to get Daniel P. Raymer's book,
"Simplified Aircraft Design for Homebuilders" and take a stab at
designing something similar. (okay, not just this book but a whole bunch
of books, along with long visits to the FAA website.)

I would buy a set of plans and use an existing design. I would
consider wood and fabric and steel tubing as well as aluminum. I would
shun certificated engines or else buy a used certified aircraft and
restore it.

Because most homebuilders today are affluent retirees and yuppies the
market has become cost-insensitive. Most designs popular today are
designed around the overpriced museum piece Lycoming engine because it
is faster and less hassle to use one.

I would leave airplane design alone until I had completed a couple of
other people's designs and done some college level coursework in
mechanical engineering or allied subjects. I have my own ideas on what
would be a good airplane but I know I'm not ready to do them yet.