Roof Pitch is the number 1 factor in roof design
A roof with a 12/12 pitch that looks aesthetically pleasing can add as much as 50% or more to the initial cost of a roof when compared to the same house with a 4/12 pitch.
Why does a steeper pitch add so much to the price? We are going to compare a 12/12 pitch to a 4/12 pitch. 12/12 has 37.5 % more roof area
12/12 roofing labor is 50 % + per labor per roofing square
Rafter and sheathing labor is 50% more
Roof framing lumber is more
Other factors that add to the increased price can include:
More attic ventilation
Increased painting costs
Increased stucco or siding costs
Roof maintenance costs, although the need is less frequent.
On the plus side most roofing materials can last 50% longer
This means that if you are going to use a steeper pitch it would be wise to use one of the better top end roofing materials available.