translate English to French: Finally, make sure that the bills the cambista gives you have his or her seal stamped on them - that way, if by chance one of them turns out to be counterfeit you can come back and complain. I have never gotten counterfeit notes from a cambista, but asking for the seal probably helps maintain the incentive for honesty.
Les compagnies aériennes proposent des prix très intéressants et un billet acheté suffisamment longtemps avant le départ peut coûter moins de 500€.