You'd have to talk to an optometrist about prices, as different contacts differ in price as well as different doctors charging different rates for exams, but you can get an exam any time for contacts, and if your last eye exam was recent enough they can use that as well.
Eye exams vary by location. Once you have a prescription for contacts, it is good for a year and you can buy contacts at any time during that one year period. For me, the exam was $100 dollars. The contacts are $28 for a box of 3 pair (6 lenses).
You can get the eye exam for free, when they run a special, but the contacts will run about $100 for the first time. You might get them cheaper if you shop around. Make sure there is some guarantee if they don't work right.