Increasing your instant and sorcery count helps, but isn't super necessary, this deck doesn't care that much about getting the 4/4 turned on quickly, so long as it happens
If you pay this additional three mana, instead of a single creature you can phase out someone's entire board
However, its worth noting that a cards competitive utility can also spike its price (even a Rare could be pricey if its a must-have in tournaments)
The borders of a card denote legality to play
I dont see any sold copies of this card on eBay (Manabarbs isnt all that good anyways), but listings are posted in the $20-$30 range
There are 15 legal Oxen you could field with this deck, and while most of them are hot ass, I expect to see this guy helm a lot of decks that run all of them