The quoted price is really too high. Following are your options:
1. Show e-test result to 5 differnt shops for feedback
2. Get quotation from 5 different shops
3. Request quotation to show labor charge separately
4. Buy your own spare part, and ask them to deliver to the workshop. Pay workshop the labor only. Ask the labor charge
5. Get the used part from junk yard
The whole exhause system could cost $1,000, depending on the part you choose. Origonal manufacturer or not should be small factor, unless it is low quality product. Minimize buying China manufacturer parts. Those are generally low quality, unless you familiar with the brand