Well the prices are going to vary depending on where you live, the doctor, the hospital, and your specific surgery conditions. You will need to consider if it's going to be Laparoscopic or an open surgery. Even though it is called the Laparoscopic band, sometimes they may have to go and open you up during surgery. This would greatly effect the cost. The web site, LAP-BAND®.com gives the price range of $12,000 to $25,000.
As far as losing weight goes, that would be up to you. Of course, you would want to be safe and not lose weight too quickly. My doctor says 60lbs. with in the first year is a safe weight-loss rate. If you want to compare to the GBP surgery however, the statistics say patients lose weight much quicker with GBP. However, from what I've read they dont keep the weight off as long.
I'm not sure about getting the band filled. I know that the goal of filling the band is to find your "happy medium." Which is just finding the correct amount of saline to put in your band that gets you the best and safest weight loss results. Also, they want to be sure that you are able to eat properly. If there is too much restriction in the band, food won't go down. And, if there is not enough restriction, food will slide right through. I've been told finding the correct amount of saline could take while. And it varies from person to person.
Complications with the LAP-BAND® are far less than GBP. The two biggest problems are band erosion and slippage. Both problems, I beleive, will require the band to be removed. (Although, I'm not entirely sure.) The best thing to do is research, research, and more research. I've done most of my research on www.LAP-BAND®.com, and by watching youtube videos. There are several videos where you can actually watch a gastric band being installed. The more you know the better! I hope this was at least a little help to you. I tried to make it easy to understand.