I agree with mogv, upgrading cards shouldn't be a flat cost. That said if it was changed to become easier to upgrade cards it wouldn't seem fair to people who put the work in to do it the hard way. That means that the cost of upgrading every possible card would need to remain the same in order to acheive some form of fairness (and even this wouldn't be ideal) meaning that some of the essential upgrade cards may rise well above 1500 in order to compensate for sparks etc.