how you know it's any leaderboard form player page?
It's true right after the sale. But I think, and it's only my opinion, that the jersey sales are calculated according the minutes each player has played during the week before the economical update. Since the minutes of the sold player will have to be redistribute into the other players, one week later the merchandising should increase.
2) Player Jersey Sales - based on NT&U21 player merchandise and player League/Country/World rankings(fully available for BB Supporters)