Some people rent them out on Ebay for about $20 a trip. I just bought one on craiglist, very gently used, for $35. I got it and it looks brand new. I'd look around before spending $75 PLUS S/H.
I'm excited to use it though. I watched the DVD that comes w/it a bunch of times...it looks SO easy. We still have to bring the carseat because we're renting a car, but the last time we flew, I was unable to unfasten the car seat both going AND coming (I have a Britax Boulevard and for some reason, my hand and the buckle weren't working together) and the flight attendant had to help me. I do NOT want to go through that again. LOL I'll be gate checking it this time! I just feel safer having her in the shoulder harness. My DD is 3 1/2and weighs 35lbs.
It's good for 22-44lbs.
from the site
www.kidsflysafe.com
Q. What is the upper age limit for children to use CARES?
A. Children who are 4 years old, weigh at least 44 pounds and are more than 40 inches tall are considered old enough and strong enough to travel without an airplane child safety belt.