Basics: I paid around $75 to join, with a one-year contract that cost $29 per month. A month-to-month contract was $39 per month, same $75 join fee.
I liked Curves; it was not far from my house, and that made it easier to go 3 times per week.
However, their exercise plan works for some people and not for others. It's very easy, but if you have exercised much in the past or are in relatively decent shape, it will not be enough of a workout. If you need to lose weight and are sedentary for the most part, it will probably work well for you.
A little OT: I particularly liked their "diet"; it's a concept that my grandmother has used for 60 years and has worked for her. Here's how she does it: she gets on the scales every morning, and if she is at or over 130 lbs, she eats next to nothing until she's back under. She is very strict about. You can imagine if you do that everyday, you're never much over that weight (maybe a pound at the most), so the "dieting" to get back to your goal weight takes only a day or so.
Curves has a diet plan based on that concept, and it seems to work. It's much more scientific and involves counting calories or carbs, but it's basically the same idea. My mother is a dietician, and I loaned her the book, and she said it is a safe way to lose weight. Her philosophy is that you have to make a lifestyle change to be your healthiest, and that this "diet" is more of a lifestyle change as optimally you would adopt the eating habits permanently.
Curves holds classes every few months for this "diet", weekly meetings and such.
Sorry about the drift...