Tell that dealer to go fu
ck themselves ... they are just trying to put money in their pocket any way they can. And you are the current mark.
New exhaust gaskets should run no more than $50 for parts plus an hour of labor. That's a $130-170 job depending on hourly shop rates in your region. A used OEM exhaust can often be found for $0-100 with a little bit of searching and luck. $2100 is FUCKIN INSANE!!