2004 Toyota Camry computer failure

I just sent my 04 Camry into the dealership for various mechanical work. They called me and diagnosed an 02 sensor problem and a bad catalytic converter. Several hours later, they called back and said that while they were doing further diagnosis, my on board computer suddenly "died" and it would cost me over $1,400.00 to replace. The car was running fine when it got there, now they tell me it won't even start. Am I being ripped off?
Thanks