You are wise to assume that insurance will not cover body lift surgery (see my answer to "When is body lift surgery covered by insurance?"). You should also make sure to compare just what "full body lift" consists of, as this will vary with each patient, the amount and distribution of the loose skin, and the exact details of the planned surgical procedure. Not all "full body lifts" are the same!
Also, make sure your cost quote considers not just the plastic surgeon's fee, but also operating room, anesthesia, garment, and hospital charges (if that is where your surgeon does this surgery.) You may be surprised to know that there are experienced, board-certified plastic surgeons who have extensive capability to do full body lifts as outpatient operations in their accredited office surgical facilities. Some surgeons (those who do not have their own surgical facility) perform this surgery at a hospital. This is certainly fine, and quite common, but is ALWAYS more costly, and exposes you to sick patients and hospital bacteria, as well as a nursing and anesthesia and recovery teams who may not do this procedure on a regular basis. Higher costs and fees are often justified by telling patients that "This is a big or serious operation that should be done in a hospital," implying increased safety or capability.
As you may suspect, I have an accredited office surgical facility (although I maintain full hospital credentials for those patients who require surgery there), and experienced staff who help me perform full body lifts in 5-7 hours as a safe outpatient procedure. My partner and I have done over 250 body lifts over the past 13 years, including removal of as much as 31 pounds of loose skin in one patient. We have performed over 16000 general anesthesia cosmetic operations over the past 23 years without death, heart attack, or stroke. Our body lift fees include surgeon's fee, operating room, anesthesia, garments, free consultation, and all recovery visits, and are around $17000 depending on the exact procedure details and time needed. I have seen hospital bills for exactly the same procedure that can be double that cost, especially when the final hospital bill arrives for the actual cost, not the preop estimate.