Coolant lights post recall repair

Hi Guys, Well we had the recall on both water pumps performed on our 08 prius with 118,000 miles on it and now we are still getting the codes. My daughter brought the car in to the dealer who said the codes were old and he is not worried about them but thinks that the radiator oring in the cap is bad (my daughters words) and they would have to drain the system, pressure check and replace whatever is bad, the troubleshooting part is $120 to start. When we got the car back originally I checked the forum and found where some of the cars were coming backl after then recall low on fluid, I checked it and ended up adding fluid and the light did not come on again for about 2 months. I am guessing if the radiator cap is bad that I would loose fluid and I could check the cap at discount auto and even put new one on. Do You think it is worth paying the dealer for this or is it just a money maker for a new radiator cap? thanks - John