Prisoner's Dilemma is one scenario in isolation, with nothing following. Steem is a system where your outcomes can be affected by other voters on an ongoing basis. That's true for both selfish voting and vote selling (sold votes can be countered the same way self votes can).
The system depends on those with the largest stake countering those who act selfishly with lower stakes. Those people have the least to gain from self voting (they are only taking from themselves) and the most to lose. Under such a paradigm selfishness is no longer the most profitable approach. People like @berniesanders and @transisto downvoting smaller players are rationally protecting their investment and changing the 'game theory' math for smaller stakeholders like you and me.
Well, a lot very much depends on a handful of individual's ability to discern the market value of things, for they dictate it, I hope for my sake too that they get it right and don't ever undervalue something
It won't take anywhere near that much for me to stop producing content of course, the economic incentive isn't there, at least not for someone with my limited ability.
Thank you for your input demotruk, appreciate it