There’s two perspectives on this. One is, as you state, extra pieces are added to initial game set-up to even the score.
Another bidding system (called the FIDA bid, initials of a number of online A&A clubs), splits the bid into at no more than 50% of the bid can be added as initial set-up extra pieces; the rest is cash to be split amongst Germany and Japan (you can give all the $ to one side if you want)
An example FIDA bid would be 15:Â inf, tank in Libya (Germany), $2 to Japan, $5 to Germany.
Actually, in FIDA, this bid would not be allowed. the Inf/tank is 8 IPC, which is more than 50% of the 15 bid. In this example, you would be able to place inf, rtl at the most.
Rolling 3d6: