[ecfisa]

Hola.

Probá si te sirve este código:

Código Delphi [-]
type
  TForm1 = class(TForm)
    Button1: TButton;
    MaskEdit1: TMaskEdit;
    MaskEdit2: TMaskEdit;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure MaskEdit1Exit(Sender: TObject);
    procedure MaskEdit2Exit(Sender: TObject);
  private
    FNum1,FNum2: Double;
  public
  end;

var
  Form1: TForm1;

implementation{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  // dado el formato que imponés en la máscara, esta línea es
  // necesaria si tenés ',' como separador decimal
  DecimalSeparator:= '.';
end;

procedure TForm1.MaskEdit1Exit(Sender: TObject);
var
  Cad: string;
begin
  with Sender as TMaskEdit do
   Cad:= Text;
  Delete(Cad,Pos('$',Cad),1);
  Delete(Cad,Pos(',',Cad),1);
  FNum1:= StrToFloat(Cad);
end;

procedure TForm1.MaskEdit2Exit(Sender: TObject);
var
  Cad: string;
begin
  with Sender as TMaskEdit do
   Cad:= Text;
  Delete(Cad,Pos('$',Cad),1);
  Delete(Cad,Pos(',',Cad),1);
  FNum2:= StrToFloat(Cad);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(Format('%f %f %f',[FNum1, FNum2, FNum1 + FNum2]));
end;
...

Saludos.