It is difficult to give a cost estimate as I do not have a photo to assess how much fillers are required to treat the sunken forehead.
However, based on average volumes required to treat forehead the amount required is typically in the region of about 3 cc at least. Based on this estimate the cost required would be in the region of $2000 to $3000 depending on the types/brands of fillers used as well as the difference in doctors' pricing.
The most common types of fillers used would be Hyaluronic acid dermal fillers like Restylane. Juvederm and Belotero or a calcium hydroxyapatite filler like Radiesse. As this procedure of forehead augmentation is an advanced technique it is best to seek treatment with an experienced doctor
