Even if @themarkymark is paying out 100% of the SBD received to delegators, he is still making money. What happens to the curation rewards earned by @buildawhale?

The bot owners can set the payout % and announce what it will be. @themarkymark could set his payout at 85% and he might lose a little voting power but it wouldn't break his business at all. It would probably improve return for the investors that stayed because smaller voting power means your number of bids to service in each round would decrease and rounds would be closer to the intended 144 minutes.

(Point 3 above is actually to create a more stable operations environment for bot operators and investors, while improving predictability for customers)