Being true i told them i am switching for Money. But then i have to convince them that i will not leave them for extra money any soon. Interesting part was when in flow i told him that "i got bored of my current job so i want to switch now" and interviewer told me that you will get bored of this company too and leave in 2 years. So i replied "I think that your Product(i got the brief about it in early round) is good enough to hold for few more years than 2"