As far as selling the biggest difference between now and then was back then software could only be shipped on floppy disks, so it was more like manufacturing, warehousing, and shipping physical merchandise.
Shareware was also widely available on BBSs by around that time although it was also distributed on floppies at Computer shows and the like. When I had a small shareware company starting in the mid-eighties the process of taking orders was still very manual--most orders came by mail with a check and I sent back a floppy (which I reproduced myself) in a mailer with or without hardcopy docs depending upon if those had been ordered or not.