Coming from IGN…

The game will be available for download on the iTunes App Store starting Oct. 7, the Wii Shop Channel on Oct. 11 (15th Oct in EMEA territories), the PlayStation Network on Oct. 12 in America (Oct 13th in EMEA territories), and Xbox Live Arcade on Oct. 13 across all territories.

Sonic 4 will be priced at 1500 Wii Points on WiiWare, 1200 Microsoft Points on Xbox Live Arcade, and $14.99 / £9.99 / €12.99 / AU$19.95 on the PlayStation Network.