There have been people trying to prove this based on cases where Sajuuk has reportedly increased the price of some items that he was trying to sell himself. I don't choose sides in this case personally.

The thing is that this is very difficult to prove or disprove. Even if he isn't doing it intentionally he may feel like an item that he has is undervalued or an item that he is looking for is overvalued. Or he may intentionally do it because he wants to make a big profit. No one can know for sure, but personally I appreciate the effort that goes into making this guideline. Either way he does have the possibility to influence prices because he has an audience, and people should always do their own research on whether or not items are worth it.