Explanation:

- Option 1: Society is bigger than economy - This is not directly related to the concept of cost.

- Option 2: Society includes polity, while economy does not include it - The presence of polity doesn't directly influence the comparison between social and economic costs.

- Option 3: Cost borne by bystanders is positive - This is correct because social cost includes externalities, which are costs not accounted for in purely economic transactions, like pollution or other negative effects impacting third parties.

- Option 4: Society includes both consumers and producers - While true, it doesn't explain the difference in costs between social and economic perspectives.