I agree with what was said above. The earned value is a good estimate when the other values are also being taken into consideration. The earned value and planned value are values to be used in theory. For example, when you are 3 months in the value should be a certain amount that is not related to budget but to what your project is supposed to be. Earned value is used to find the schedule variance and not to see if you are over or under budget. However, when it comes to cost variance I think there could be some misrepresentation of over or under budget details. Since EV is an estimated worth based on overall budget and not on specific task budgets the cost variance could show that you are under budget when the next step is the most expensive.