Building a mono-green deck around this is an easy way to cheat huge creatures onto the board, with the likes of Ghalta, Stampede Tyrant offering even more value for their entry
Apart from pricing at retail, two of the most common reasons I've found for why sellers overvalue their cards is that they don't realize that some of their cards have been reprinted, or they are pricing from memory, often at a card's peak price
Chief Engineer $2.50 Affinity doesnt want this card its spells are cheap enough already, and it always wants to be attacking but the potential is certainly there for some kind of midrange robots deck in Modern
While the latter effect is nice, the main reason to be playing Archetype of Aggression is the former effect
Which means you can probably instakill at least 1 player, but if you have 1 or 2 more Slivers that should be enough to kill everyone off