My laptop is 'vintage', meaning that even the Apple store doesn't have the replacement parts. It stopped responding to my efforts to turn it on after a few months of occasionally being coaxed into starting up.
I took it to the Mac Shack where I bought it used. They charged $45 (!) to diagnose the problem as being the logic board.
Today I took it to the Apple store where they didn't charge me a thing but told me they couldn't get the parts anyway. The Apple genius said that it could be the logic board or something else and which is cheaper to fix, but "you could take it to the Mac Shack and they would charge you 1/2 hour of labor to actually open it up and tell you the exact problem." Good to know.
picture from homepage.mac.com