Well, I understand why they aren't cheap, and they shouldn't be. After all, players should earn those upgraded cards, and it gives players a goal.
However, I do think that 1,500 electrum per upgrade is a bit prohibitive for players. It can take a bit of time to understand the play of the game and to build up a solid deck for a player's style.
Instead of making it a flat 1,500 electrum per upgrade, why don't we stagger the cost of upgraded cards? After all, normal cards have differing prices based on differing power levels. We could do the same for upgraded cards since an upgraded pillar is not nearly as powerful as an upgraded permanent.