For the most part he only does one thing the turn you make him and that is producing a 1/1 and not gaining any loyalty
This innocuous gobbo is one of the very best enablers for spectacle cards and Rakdos himself, doing what Lobber Crew and Nettle Drone do at only 1cmc
Third, pricing is clear and flat: $17.99 for a single card, packs up to $49.99, free US shipping
Secondly and perhaps more importantly is the hype this card is receiving from the player-base
When building a list of the most expensive, you have to refine your discussion to either include or exclude these three sets, as you would never make it to a consideration of the expansions or later traded cards without excluding these
Assuming no one will pay two to stop you, you will be getting at least three mana per round