just my 2cents opinion...
well since seller already assumed his motherboard faulty and expected only rm30 from his buyer... then seller just accept it lah and move on. if your buyer mesg/pm you back and confirm the motherboard is working you just consider that additional rm30 as bonus loh. why you wanna so desperate with that socalled 30+30? remember your 3rd person offered rm30 only and then came 4th person who offered you rm30+30 and you changed your deal and sold it to the 4th person.

now you wanna complain about that 4th person didnt reply back to you.

wah seriously you got an attitude problem there my friend. come on lah you already sold that motherboard and now you wanna recomplained again because another person told you that your ex-motherboard can be fix only small matter. so now you said you felt like beeing con? what is this?

my advice to you if you already make a decision selling your item and sold it already then just stick to that earlier decision. this is not something like in the movie "back to the future" and you can go back and change all the decisions. if like that everyone sure millinaire already by now!