[XK]

Make it:

pawn Код:

if(GetPlayerMoney(playerid) >= 500) 
{ 
    GivePlayerMoney(playerid, -500); 
} 
else if(GetPlayerMoney(playerid, < 500) 
{ 
    SendClientMessage(playerid,-1,"you don't have Enough cash to buy this weapon!"); 
}

and as Misiur said,you are missing to close it,put )