Because these codes are no longer manufactured, they are considered rare collectibles. ~$20 (1,600 Microsoft Points).

Amazon contain DLC codes, but these must be brand new and factory-sealed to ensure the codes haven't been used. Reddit +6 Expansion Content Overview The Rally Expansion Pack, originally released on December 18, 2012, transforms the Colorado setting into a dedicated rally championship. YouTube +1 11 sites Rally Expansion Pack | Forza Wiki | Fandom Price. 1,600 / $19.99. The Rally Expansion Pack is an expansion for Forza Horizon that was released on December 18, 2012. The expa... Forza Wiki

Despite being delisted, there are a few specific ways players still experience the rally content: I really want the Rally expansion but can find a code

While some third-party retailers like GameStop or Amazon occasionally sold digital codes for the Rally Expansion after delisting, these stocks have largely been depleted.

(not a paper):

Finding a digital code for the Forza Horizon 1 Rally Expansion

The Forza Horizon 1 Rally Expansion Pack is a beloved piece of the franchise's history. While the days of easily buying a code on the dashboard are gone, those who redeemed their codes in the past can still enjoy the dirt trails of Colorado. For those hunting for a code today, proceed with caution, keeping in mind the closure of the legacy marketplace and the game's "End of Life" status.

: Many codes sold today are already redeemed or expired. Microsoft support cannot generate new ones.