The Performance Suspension for the E90 is ~US$1,500 so it seems reasonable it would be priced similarly for the F30. I seriously doubt that BMW would sell stiffer and shorter springs without dampers to match the higher spring rates and shorter suspension travel. It's not clear what is included based on the description in the catalog (pg. 5 of the PDF below), but it sounds like it will be dampers + springs, etc.
The September release date is listed in the M Performance catalog on p.9 of the PDF.
M Performance Parts Catalog PDF