Does the cost of cheek implants increase if I want to get a size upgrade from the ones I have already?

You might want to ask your doctor if he/she can augment your cheeks with fat grafts.  It is usually more effective, and longer lasting, than other fillers and less invasive than replacing your implants.

The price of Cheek Implant operation depends on several factors such as the difficulty of your case and your request for your operation area.

I’m glad that you’re enjoying your cheek implants and it’s not uncommon to want to replace them for a different size.  The cost of a cheek implants, whether it’s an initial procedure or replacement, is dependent upon which type of implant you would like to replace your current one with.
Standard cheeks implants cost approximately $500-700 for the pair and do not change in price between small, medium, large and extra large.  If you’re looking for the same design but larger, you should expect to pay the same for your replacement surgery as you did with your initial surgery.
If you’re looking at getting custom cheek implants, the cost of the actual implants would be considerably higher.  In addition to the custom implants costing approximately $4000 for the implants alone, you would also have to take into consideration the cost of a CT scan and design sessions along with the facility, anesthesia and surgeon’s fees.  The total cost for custom cheek implants will cost approximately $10,000 to $15,000 total.
I hope this helps!

The cost to remove your current cheek implants and replace them with a larger size would really be at the discretion of your surgeon.  It is possible the cost could be similar to what you paid to have the current implants placed or it could be more.  

 Hi, I have performed many Cheek Augmentations with cheek implants to shape the cheeks for over 30 years.  The cost for cheek implant removal and replacement (at least in our office) increases over primary placement cases because they are more difficult to perform.  The tissue is more difficult to dissect, the existing cheek implants must be located and removed gently (so they remain intact and don't leave a broken segment inside the tissue), the implant pocket must be developed especially if the existing cheek implants are too small. 
 For all of these reasons we charge more for revision cheek implant cases than for a primary cheek augmentation.  Whether the cheek implants are size medium or large and 3 or 4mm does not affect the price.  Specific costs can only be provided once a thorough history of what was done previously is obtained as well as existing in person or photos and an electronic consultation has been completed.
Hope this helps.