Last I heard a couple a bucks a bag was standard for major airports. Up to $5 if a bag is exceptionally large or heavy. IMHO a fin would be about right for two average bags.

On the there hand some of the skycap and porter trade is a shakedown with the guy grabbing a hand bag, tossing it into a cab and smiling with his hand out. Sort of like the squeegee guys at street corners. They do nothing, or next to nothing, sometimes less than nothing, and then guilt you into a tip.

There are some that do real and useful work speeding people and their bags securely through the crowds. The best have connections with the cabbies and security so you get a good driver and move swiftly. They also coordinate with other passengers and drivers to make the most efficient use of time and space so you save money. A service well worth $20 or more.

But for every good one there seems to be at least one that is running a shakedown glorified by a hat and jacket.