The scanner identifies the card from a photo, and the value checker uses that identification with condition signals and recent market comps to estimate what the card is worth
Legality depends on the tournament format -- The Five Stages of Grief can be legal in some formats and banned or restricted in others
Though it's impossible to say why sales like these occur, as there are a variety of factors that could contribute, it's clear that they don't always make sense
Where did they come from, who are they, what happened to them
But they have also removed a bunch of cards that dont meet the modern standards six cards to be specific: Contract from Below, Darkpact, Demonic Attorney, Earthbind, Crusade and Weakness Finally, to add a bit of sugar, spice, and everything nice for flavour, they have also added text to it