Just bought Ace Combat: Assault Horizon for $9.99 (£6.85) from Amazon US, activate using steam.
http://www.amazon.com/Ace-Combat-Assault-Horizon-Online/dp/B00B4Y7OP0/ref=dsvbl_item_0
They are also doing a Cars, Jets and Dirt Bike Pack for $16.99 (£11.65)
Ace Combat: Assault Horizon, MUD - FIM Motorcross World Championship, RIDGE RACER Unbounded. All activate using steam.
http://www.amazon.com/gp/product/B00BR0Q0II/ref=amb_link_372816042_2?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=right-1&pf_rd_r=01V5GHXC65261XZH4VS6&pf_rd_t=101&pf_rd_p=1515239862&pf_rd_i=979455011
http://www.amazon.com/Ace-Combat-Assault-Horizon-Online/dp/B00B4Y7OP0/ref=dsvbl_item_0
They are also doing a Cars, Jets and Dirt Bike Pack for $16.99 (£11.65)
Ace Combat: Assault Horizon, MUD - FIM Motorcross World Championship, RIDGE RACER Unbounded. All activate using steam.
http://www.amazon.com/gp/product/B00BR0Q0II/ref=amb_link_372816042_2?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=right-1&pf_rd_r=01V5GHXC65261XZH4VS6&pf_rd_t=101&pf_rd_p=1515239862&pf_rd_i=979455011