I think there are some ways to avoid this. To be honest I have not completely researched this and neither completely calculated it through because I want community input on these things first before I dig deeper into it.
An easy way to avoid this is to base curation not only on how close someone got to the actual result but also on how big the distance was between after the own vote and the final result.
(After I voted 1$ it got to 1 out of 20$ (final result) which is a bigger distance than after a whale voted 19$ and got to 19$ out of 20$).
However, I do think that the general approach is
a) Less controversial than downvotes
b) More what we actually want.
So in the provided example the bettor/curator would receive a larger curation reward for their $1 bet than the whale's $19 bet? Not sure I understand how you mean this.
It would get a larger relative curation not a larger curation value. The 19$ bet could still get 5$ curation (around 25% of the bet) but the 1$ bet could get 50 cents (50%)
Well, that's definitely preferable to the extant system, IMHO. At least it supplies a superable reason for curation rewards.
I'm not actually sure that is where we need to aim, TBQH, but it's sure food for thought.