This is one area that I specialize in. Custom one of a kind quilts.
#1 Depends on the complexity. A queen size double wedding ring, piecing only, starts at $800 but a queen log cabin starts at $400.
I start my calculations at 25cents per square inch, add 25% for extras, quilting etc.
Tshirt quilts go for $25 per shirt.
One thing you need to take into consideration, you charge according to what your community will pay.
I tell my customers to give me at least one month. That can go as high as 2 months depending on what my longarm business is doing at the time.