Based on your level of obesity, it is very unlikely that your skin will "bounce back" into place after bariatric surgery. As a post-bariatric plastic surgery specialist, I have worked with countless post-bariatric clients, all of whom were left with sagging skin. That being said, it is your choice whether or not you choose a cosmetic procedure to improve your body contour after weight loss. Plastic surgery is by no means mandatory but the excess folds of skin can interfere with daily activities and make it difficult to find clothing that fits properly. If the excess skin causes chafing, rashes, or other medical problems, insurance will sometimes pay for part or all of the corrective surgery.
If you do decide to save up for plastic surgery, it's important that you select a board-certified plastic surgeon who has many years of experience with post-bariatric cases. I understand that price is a concern for you but I highly advise against choosing "bargain surgery" to save money. In the long-run, the risks and potential complications from an inexperienced surgeon could cost you much more.