Last month I picked up my parents returning from India at New York JFK airport. That's when I learned that the luggage cart rental has been increased there from $3 to $5. This apparently happened in February 2009 at both NYC airports.
Welcome to the US. Most fellow passengers of my parents were quite upset, and many avoided using the carts and struggled with their bags. Back in the late '80s and early '90s this charge was $1 to $1.25. I suspect Smarte Carte, the private company that operates and rents these carts, has a pretty cozy relationship with the airport authorities. This company's website as well as JFK's official one studiously omit disclosing these rates.
The parallel between these cart charges and non-universal US health care (at least as it existed till today) is obvious. It also points up the inefficiencies of this private, fee for service arrangement that makes everyone except this private company worse off. While passengers are being ripped off we also may be nearing a high cost death spiral as also explained by Krugman in a health care context. That means the exorbitant cart rates will decrease demand for them so much that the overhead costs will be spread over fewer carts, creating a push for even higher rates.
In all airports outside of the US luggage carts are "free", meaning these are included in normal airport charges that should work out to a few cents per passenger. So almost everyone uses carts and the per unit cost is a small fraction of that here. It's high time the airports (like health care authorities) learned from such better practices outside the US.