Like most Magic: The Gathering cards, the value of Glaring Fleshraker depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Modern Horizons 3)
It also has quite possibly has the most "out-of-game" interactivity of any card printed in any card game ever made
Drawing is drawing
you never want to pay the full to cast that measly 4/4 flier
The third trick, which shows up on Glory-Bound Initiate, is to do what we call "inverse addition," where you take two different numbers for power and toughness and then have the boost be those two numbers swapped
Part of the issue for these players is that while some decks can make use of their graveyards, for those that don't, the counterplay against Mill can be hard