Q: Macbook air logic board failure

I have bought macbook air in March 2015. Until 2 weeks back it was working fine. Suddenly it got switched off one day and doesn't power up at all. I have tried all the troubleshooting steps given in the apple support pages. As it has been just 1 month over the warranty period of 1 year I will not get a free replacement or repair. Then I took it to the apple authorized service center, they examined the macbook and told that logic board is not powering up due to some technical failure and it needs to be replaced. He said that it will be charged around 40,000 INR ($590) . When I asked him why this has happened, he gave a reason that it might be because of power voltage fluctuation. I don't understand why on earth an electronic device will be damaged when it is powered with the adapter. My adapter is working fine. The whole purpose of using an adapter is to protect the device from this kind of voltage fluctuations. Now I have nowhere to go but to just throw that piece of crap (macbook) in the store room. I completely regret for buying a mac and will never go for apple devices again in my life.

Any suggestions for my problem are welcome.