With the increased popularity of cosmetic surgery, there is now increasing competition in the marketplace for patients. Most patients will consult with several plastic surgeons before narrowing their search criteria and settling on one or two who have made the final cut, as to which one will actually do the cutting. At this point, the fee may make the difference between chosing one over the other, and patients may be tempted to "wheel and deal".
However, I believe the decision of who performs your surgery shouldn't be based solely on the fee differential, and it is unwise to attempt to compare apples to oranges. Factors to consider include the experience level of the doctor, the environment in which your care is rendered, and the level of trust you develop in one doctor vs. the other. If you feel more strongly positive about the less-expensive doctor, there is no problem and no need to negotiate. If on the other hand, you feel better about the more-expensive surgeon, should you ask for a discount?
If the surgeon wants "your business", he most likely will offer you some incentive for booking your surgery, such as built-in discounts for each additional surgical procedure performed simultaneously, or perhaps by offering to cover your stay in an aftercare facility, or by giving you a reduced fee for injectables, Botox, or other office procedures.
It is unwise to directly question the fee structure of one surgeon vs. another in the same way you wouldn't ask the Mercedes dealer to match the sticker from the Kia dealer. If you are hunting for bargains, don't expect Filet Mignon treatment on a hot dog budget.