The more experienced the players (particularly Axis) are, the greater the need for the bid. 2nd edition favors Axis but only when Axis knows how to exploit their advantage.
If the Axis player is inexperienced, then they won’t know how to expand quickly and efficiently…so it could be unnecessary to have a bid because the Allies will have more income.
If the Axis player is experienced, then they will know how to expand rapidly. They’ll also be aware they only need to win on one side of the board.
If both players are advanced, a fair bid is at least 20 and could be as high as 50 for an optimally balanced game (depending on the bidding conventions being used). But with inexperienced players a bid that high might seem excessive.