uses DateUtils;
var StartTime: TDateTime;
procedure Start;
begin
  StartTime:= Now;
end;
procedure TimerOnTimer(Sender: TObject);
const CostPerSec = 5000 / 60;
var TempCost: Float;
begin
  Panel1.Caption:= FormatDateTime('hh:mm:ss', Now - Start);
  TempCost:= SecondsBetween(Start, Now) * CostPerSec;
  Panel2.Caption:= FormatFloat('Rp. 0.00', TempCost);
end;

@DelphiExpert: const CostPerSec = 5000 / 60