Ssorry, we dropped the price on steam some time ago and forgot to update it on itch. both stores are now $4.99, thanks for bringing this to our attention!
the itch version and the steam should be the same. I believe the steam version does require you to have Steam running/installed, as we hooked up alot of achievements/etc from Nova-111 onto steam servers. If you wish to have the DRM free one, you can buy it off Itch
