I know of no fairer way than supply and demand to dictate rates in a free, market-driven economy. A hotel is worth less on a Tuesday night than it is on a weekend. If you don't believe me, just try to get one in the same city as the next Super Bowl for that very weekend. I bet you could get it for a lot less right now.
Trucking in the spot market, that is the 10% or so of trucking that happens outside of the contract market, is heavily affected by supply and demand. The contract rate for certain lanes and truck types are a guide, but the simple law of supply and demand tells us what a truck is worth on a particular day, in a particular place.
One of my best paying loads in the last 6 months was last week. I had a truck positioned in the right place to move two 8' steel castings for a rock crusher that went to a rock quarry. The load was tiny on my 53' step deck, but it did weigh 18K#. It's hard to believe that this little load paid more than some of my recent over-dimensional loads that are worth hundreds of thousands of dollars in product value. Being in the right place at the right time makes all the difference. Study the rates in your preferred lanes and learn to have your truck in areas of high demand.
The law of supply and demand is often displayed very clearly in the energy sector. Here recently, I've noticed numerous ads on Craigslist where energy companies in the oil fields are trying to hire drivers. Some are offering free housing for the employee, while others are offering relocation assistance. And this is all while offering wages that are more than double what a driver could get in a normal market, away from the oil fields.