Whats a ballpark price for an extended warranty? Say for a 2000 C5 Corvette with 23k miles.

I got a 100,000 mile warranty for my 01 Civic for $500 I believe through the dealership.  I think that if after 100K if you don't use it you get half of it back.  I have had to use it though when my turnsignal relay box thing melted and they had to tear apart the whole dash and rewire it.  If I had to pay out of pocket it would have been around $900.  So I paid them $500 to save me $400.