Airplane design.

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.)

http://www.aircraftdesign.com/sadfh.html

I put into Raymer's spreadsheet a few things like 619 mile range, max
speed 160 mph, payload weight of 1190 lbs, wing taper ratio 1.0 and I
get a whopping gross weight of 4322 pounds, not the 3000 pounds of the
Murphy Moose. The engine suggested by the spreadsheet was also huge.

Well, that's a bit of a disconnect. I got similar disconnects when I
put in sizing data from other airplanes. The Raymer spreadsheet gives
much heavier designs. What's with that?

Q1) Is this because the Raymer book recommends overbuilding so that the
typical home designer doesn't have the engineering skill to make it lighter?

Q2) Are there any better books out there?

Please be kind. I'm a very sensitive fellow. (HA!)