There are multiple treatment options for the treatment of "sun spots." Cost depends on the type of treatment chosen, the area you are treating, and who is performing the procedure. Chemical Peels, IPL, and laser therapy such as Fraxel or Active FX are all options for the treatment of sun damaged skin.
Chemical peels tend to be more affordable and can do a good job depending on the type of skin you have, the strenght of the peel, and the amount of downtime that you are able to tolerate.
IPL is a light photorejuvenation system that does a wonderful job for the treatment of "sun spots" on areas of the face, neck, chest, arms, and hands. The price of this procedure varies according to who does it (physician, nurse, physician assistant) and location (medical spa, medical office, etc.) . There are also lasers that can be performed to reduce sun spots and improve the overall texture of the skin.
Overall, the price depends on the choice of treatment, who performs the procedure, and how aggressive you want to be. Prices acan range from a few hundred dollars all the way up to a few thousand dollars. I would recommend meeting with a physician or someone extremely well trained to discuss your skin type, goals, and amount of downtime that you can tolerate.
Good luck refreshing your skin.