I THINK every 12 hours they see what the AVERAGE price for that item has been selling for and make it that... E.G. DDS, 48k-52k.. But majority gets sold at 48k. So next day they are 46k-50k... Etc.. dds are currently 30k each though..Because They are hard to find.. people try to search "DRAGON DAGGER" not "drag".. it only comes under drag.. thats why its dropped heaps.. but as for ur tuna, it just goes on the average selling/buying price.