Depends on where you get them, some salons offer Brazilian from 50-60 and others offer it from about 90-120. absolutely depends
And how long it lasts absolutely depends on how hairy you are and if you used to shave and stuff like that. On average it'll be last sometime between 2-3 weeks.
Another piece of advice is to look up the salon and their ratings on yelp or something and the person who's gonna be doing the waxing, make sure they are good and talk to them before they start waxing and tell them exactly what you need!
Brazilians range from as low as $20 to as high as $70 and full body waxes typically cost anywhere from $70 to $180
This is all dependent on where you go :P
How long they last is generally anywhere from a month to 2 months. Everyones hair grows at a different rate, so if you're the type of person who gets waxed and 3 weeks later the hair is back, that's just how you are. But since waxing pulls the hair from the follicle, the results typically last around 6-8 weeks