How much does a power button replacement cost in general?

So, the power button of my GNex decided to stop functioning about three weeks back. I had set up an 'Event' in Llama to turn on the screen whenever I plug in my headphones. And I had also cut out the 3.5 jack from an old headset cause I can't be plugging in the entire set constantly.

So far, Llama has enabled me to use the phone even though the power button doesn't work but then I tried to take a screenshot and damn, I couldn't. I had totally forgotten about that. I took the phone to Samsung and they say it'll cost over 15,000 Rupees. I took it to several unofficial dealers and they say it'll cost over 10,000.

Seems to me like a bit too much. How much would the cost of repairing it actually amount upto?

I live in Sri Lanka btw.

1 US Dollar - 126 Sri Lankan Rupees.