Parents can be added as dependents within the residency application, by providing the solvency required per dependent, and recent authenticated official documents to prove the family relationship, such as your wife´s birth certificate. The additional costs and fees should be for each parent, similar to the ones related to each of your dependents, such as your wife´s cost within the existing application.
It depends on the type of visa you will apply. However, please note that your wife should apply as principal, not as your dependent.
An applicant may include their parents (children under 25 years old and spouse) as dependents. And in order for his or her spouse's parents to be included as dependents, the spouse must apply separately to a residency permit as the main applicant.