[notime]

well, the "new integer:money" is useless just "new money" is enough
then, money is always 0, because you didnt define what money is
try:
money = GivePlayerMoney(killerid, -(GetPlayerMoney(playerid) / 50));
then it will work.
oh and the "you've lost %d money" doesnt make sence because now your telling the killerid(who should be rewarded) losses the %d money.
so that should be playerid instead of killerid