Regarding pitch and it’s cost, the roof is pitched more for several reasons:
A) we can have a better view up
B) HGs can worry less of hitting roof while going donw the stairs
C) rain and dust etc flow off better when more tilt
D) heat from roof is less due to more distance to higher ceiling
E) heat flows up faster and generates some backdraft
F) smoke from the BBQ can escape better
So the $3500 are for the more material due to more pitch of roof and also the load baring.
We believe that these are good enough reasons to add more pitch (and thus cost).