Toyota Repair: Avalon 97...leaking gaskets?, transmission flush, gaskets

Question
I took my car into a dealership for a transmission flush and they claimed I had two leaking gaskets. repair would be $450. That seems like of money for two pieces of rubber.
First off, what exactly are they referring to? Do these keep oil from seeping out?
Second, is the price excessive?  

Answer
Without more information from you I have absolutely no idea what gaskets they are talking about either, you need to ask them what gaskets they are referring to and maybe I can tell you if this is a reasonable cost for the repair, right now I'm as lost as you are.