cost of a diagnostic anyone know?

so i went to GM and asked them how much it is to remove the Anti theft on the engine light so i can start the engine

but they wont let me they insist a diagnostic can take from 2 min to 2 days and they cant even give me a realistic answer

all i wanted was the perment anti theft removed from the computer like erase code that its on as the 3 key 10 min thing does not work for this car even when i chang out the key cylinder

is there a place i can get what i want erase this damn code?
cuz i told another gm place i dont want no high price or i scrap car

like if its a 1000 bucks they can have the car

its for a 1997 cav 2.2