Generally what percent of laptop cost is its motherboard?

My Asus notebook is acting weird these days. It just shuts down that's it! There is no temperate issue and I ran memory test that was ok. Hdd is also good. Generally in my observation such issues occur when motherboard goes faulty.

I will take it to service center but I suspect they will suggest to change the board. Generally any ideas what is the proportionate cost of motherboard in comparison with laptop. In my notebook RAM is integrated on mobo so I suspect a heavy toll.