If it's just a crash cam then as badger says £9.98. If you want decent 1080p footage of rides to edit, etc then stretch to an SJCam M10 (SJ4000 in a much smaller package).
This is footage from a cheap one (shot at 720p the 1080p option is not genuine 1080) https://www.youtube.com/watch?v=MkzBGMuUAc8
This is from an M10 at 1080p https://youtu.be/1vhE3X-3eUA?t=45s