FIA must deliver a clear and just response to instances like this where one team has gained an unfair advantage by breaking the rules. A strong punishment for Red Bull for overspending will deter other teams from future violations. In addition, the financial rules must change - $7M represents a massive upgrade on an F1 car, not a "minor" breach. Team leaders must have greater personal responsibility for finances.
The FIA can't be too lenient or will risk creating a precedent that would end the budget cap. But making an example of Red Bull also isn't the right way to solve this issue. Too harsh a punishment would trigger a costly legal battle that is likely to tarnish the organization and Formula 1 itself. The FIA must walk a fine line to get the sentence right, bearing in mind that this was just the first year of these rules.