You don't break even by winning 2, by winning 2 you just buy a pack with the 500 gold gone.
You need to win 5 in order to actually come out positive and 6/7 to profit from this.
The reason for this is because gold is more valuable than packs because gold can buy packs from future expansions and if you don't need anything from this expansion anymore you're effectively burning gold for no reason unless you win 5+ to come out of this pit with a profit.