I think you've missed both issues...
1) The one who got to the 5th place put more money and more important more effort to get to this place.
Why should he get less?
It also could lead to a team lossing just to be in this RL round, and this is not a realistic scenario.
If I need to think on a solution regarding it, I would say that a prize, upon team's place at the week before RL/PL round starts, is needed to be given.
This is another way for making it more reliable to the "real world".
Basicaly it is absurd that a higher team will earn less.
BTW, in case you are in my situation that you are winning from current situation you don't need to fear, as it will cannot be assigned on current season.
2) I'm not saying playing less.
I'm saying that under current total games limitations, the regular season is better shorten for a longer (and fairer) RL (and PL) round.