Nothing to do with leaderboards, it was because back than new items got added to the shop from time to time, some with pointless cosmetic fluff and others that had actual stuff behind it.
Rich users could just buy it instantly, because their daily interests covered it without any issues and thus finding a price was difficult, because it was supposed to be affordable for new users but should not be a no-brainer for richer people. So the prices for some items and ranks were stupidly high... like they are right now too for other reasons. Because some few can easily make coins in the Lurker Thread, it is seen as the default income and thus the price is set so ridiculous high.
At least the price for Members+ was halfed, it was 5K not long ago. Can you even believe it was only 450 at the beginning of the year for permanent Members+?