Auction House Price Manipulation

Looking for feedback from the community on this phenomenon I've experienced. It seems like there is someone, or multiple people, who always and seemingly automatically re-posts single mats like this for close to half the price in attempt drive down the cost, then scoop those mats up to resell at the higher average price.

Is this accepted? Do I just keep buying their single mats at a profit to correct the market cost? Do you report people for this?


Edit- To add photo