Correct me if I'm wrong, but this sounds like a lottery, where the lottery ticket doesn't expire after the first drawing. So as time goes on, the pool of ticket holders increases, and the effective payout drops, because the probability of "winning" keeps decreasing.
If that's right, the lottery owner will receive increasing funds in the beginning, but as time goes on, marginal revenue will level off and then go on a steady decline.
Isn't it all about the odds? Spinbot will accept up to 10SBD/STEEM per day and will credit you with it, increasing your probability of winning its affection (upvote). But 2 days per week it will upvote completely randomly adding a socially progressive element (robinhood like even..). Investment made in the bot will cover expenses (for delegation, hosting etc...) and be reinvested into making it even stronger. There is an inflationary element but what if you had a 1/1000 shot of winning 100$ twice per week and it only cost you 1 steem to get in the game? Do you feel lucky?
You might be right. I didn't go into it as deep. There are the two days where everyone has the same chance though.