I'd be surprised if 50,000 of them were all just autovoting accounts!
@penguinpablo's post from today shows that there are about 50000 posts being made per day currently. I doubt that the average number of posts made by an account is 10 per day. Maybe someone has 3rd party data to show exactly how many accounts are actively posting.. I just looked through a bunch of different apps from steemprojects and couldn't find that relatively simple data.