Why is it so expensive to replace a ruptured implant?

In many cases surgery fees are based on time. Removal of scar tissue for capsular contracture usually does require more time than it takes to perform a first time breast augmentation. Two hours is not an unreasonable estimate for surgical time. Thank you for sharing your concerns. Best wishes.

When it comes to costs of surgery, there may be many “variables” involved. The specific surgeon's credentials/experience level (or lack thereof), the specific geographic area you are looking at, the different operations available, the location of the procedure (quality of surgery facility), type/quality of anesthesia provide… are some of the potential variables involved. Undoubtedly, the complexity and/or lenghth of the planned procedures in your case, may  explain the costs of surgery. You will find some average costs of surgery listed on this website and on individual plastic surgeons' websites as well.
In regards to outcome of the planned procedure, more important than costs of the procedures will be careful selection of your plastic surgeon. I would suggest starting with the American Society of Plastic Surgery and/or the Aesthetic Society of Plastic Surgery to obtain a list of well experienced board-certified plastic surgeons.
Then, I would suggest you visit a few surgeons whose practices concentrate on aesthetic surgery. Ask to see lots of examples of their work and preferably speak/see patients who have had similar procedures done.  I hope this,  and the attached link ( dedicate a revision breast surgery concerns), helps. 

You did not describe what type of silicone gel implants you plan to have. Textured round silicone gel implants and anatomic silicone gel implants are more expensive than saline implants and smooth round silicone gel implants. Removal of scar tissue, or capsulectomy, is indicated if there is surrounding scar tissue that has distorted your previous implants or made them feel very firm. Replacing implants along with capsulectomy is a more difficult and time consuming procedure than the original operation to place the breast implants. You did not provide photos or other information to determine if you might be a potential candidate for a breast lift. If you are not satisfied with the two doctors you saw then consider a third opinion from an experienced plastic surgeon certified by The American Board of Plastic Surgery. Good luck!