golf.scala

val cost: Option[String] = Some("123")
val method: Option[String] = None

(cost, method) match {
  case (Some(c), Some(m)) => Some(s"$c $m")
  case (Some(c), None) => Some(s"$c")
  case (None, Some(m)) => Some(s"$m")
  case _ => None
}

shorter.scala

(cost, method) match {
  case (None, None) => None
  case (c, m) => Some(List(c, m).flatten.mkString(" - "))
}

shortest.scala

List(cost, method).flatten.mkString(" ").some.filter(_.nonEmpty)