what gaskets are they changing? sight unseen?
go get a real estimate for the leak.
valve cover gaskets are about 40
some times the oil pan leaks, they would rape you on the labor, but a lot of the time you think its the oil pan and its the valve covers leaking.
oil pressure sensors leak too, they cost about 12 bucks.
could be any of these things. these are rough prices for you to buy the part, your mechanic will add 20 % to that price, and then add labor.