Card Ladder

Can please somebody help me understand how Card Ladder works, as I don’t understand the value Fanatic/Card Ladder use

Looking at Pikachu Van Gogh PSA 9 cards sold last week, they are ALL above 300$ on ebay. Card Ladder value was 330 on tuisday, yesterday if fell til 306, today it is 265. Is Card Ladder trying to get the price to fall or what, I sold both mine on Fanatics for 395, so i’m happy, but don’t understand how the value is put.

It’s fustrating that i list cards with the 20% above to get the 6% fee, but the value change every day, so it’s hard if keep price up to date with listings