Rick,
I went through this a few years ago (full set of cushions though) and I was absolutely shocked at the prices quoted by the professional shops. They ranged from $4K to $5K for a 15 cushion set. There was no way I was going to spend that kind of scratch on a set of cushions, period.
My solution was to provide a project for our local school district shop class facility. They have auto upholstery classes there (they've done 2 cars for me in the past, very nice work). I provided all the materials, patterned the cushions and they did the rest. I kept it simple, no pattern in the fabric and plywood backs so the students could use their staple guns (it happened to be my preference anyway).
I'm completely satisfied with the result. The fabric and thread is synthetic, the staples are stainless, the foam is new and the stiffness I want, the plywood backing is covered with vinyl. Total cost out the door including a monetary gift to the class was $1500.
The instructor kept a close eye on everything. My strategy was to have them do the project near the end of the semester, sort of use the project as a final exam. The students are much more experienced that way. And the instructor was thankful to have a real world class project.
Here are some main cabin pics of the finished product: