It would be interesting to do an analysis of certain types of 'quality posts' (above a certain research, length, grammar threshold) and see how much more they get paid compared to lower quality posts (measured by the same metrics)
You'd have to compare the same author - because likeability, the wealth of your friends, the value of your account (money follows money) all have a larger impact.
My feeling is that there'd be a marginally higher payout on the quality posts.
Or maybe not, I had a quick scroll through exlye's posts - his 'here's what I did this evening' posts seem to get paid just as much as his 'here's some analysis of steem posts' - the later being much higher 'quality', I mean unless you want to argue the toss that a picture of him with a steak is worth more than a 10 minute reflective vlog on SBD prices.
Actually pay varies quite a lot. Of course it's always above $20 because of his early adopter steem friends.
OK he's not representative, but based on his post payouts quality has very little to do with rewards.
@trufflepig suggests the same.