Check labor costs in your area. My guess would be that your local auto shop charges something like $85/hr. If material cost are $100, then you're looking at about 16 manhours. Probably not out of line. The only way to beat that is to buy your own sewing machine & provide your own labor. A bimini and sail covers are not tricky jobs - certainly not like a dodger (which I finally got up the courage to try - came out pretty well).