Isn't everything in this world equal in value? Can we say that the value of a human being is greater than the dust?
Your question reminded me of this Zen koan
There once was someone who asked Ch'an master Ts'ao Shan, "What is the most expensive thing in the world?"
"The head of a dead cat," was the answer.
"Because nobody gives it a price."
Commentary: By using the image of a dead can, Ts'ao Shan tried the destor the common virtues of the ordinary mind. On the other hand, [etc.]
That might be memorable or striking -- but I didn't find it easy to understand when I first read it.
There appears to be some explanation of it here (but beware that people say that explaining a koan will spoil its effect on the reader). This explanation seems to criticise the master:
In his book Pointing at the Moon , Alexander Holstein offers an explanation to the above mentioned answer of Zen master, as being his attempt to teach his disciple to “destroy the common values of ordinary mind”.
As it is evident in this teaching, the answer to “what is valuable?” - was answered here based on “what is not valuable” in the ordinary view of people. Zen master of this koan does not know how to answer a question on what is valuable in Buddhism, and takes what is regarded as not-valuable (in the mind of common people) as a reference to say something.
Additionally, the master’s aim to “destroy the values of ordinary mind” - is non-Buddhist in essence. Nichiren teaches, that the ordinary mind of ordinary people (of the Nine Worlds) contains within it the Buddha mind (Buddhahood) as well.
I think that's saying that to ask "What is expensive?" or "What is valuable?" is ordinary and unenlightened thinking -- i.e. what I might think of as, "the wrong question to be asking".
There is incidentally a proverb or idiom in English (not Buddhist), "The best things in life are free."
Someone might say, “The best things in life are free” to celebrate something that he enjoys that has no monetary value [...] for example, after spending a day on a hike through nature
Someone can also use this phrase as a warning, [to] indicates that a person is forgetting about the things that truly matter in life.
The phrase the best things in life are free expresses that happiness comes from places other than money and objects.
I think that may normally be non-Buddhist if it involves delighting in and attaching to experiences, but even so.
I'm not sure whether this is inline with Oyamist's answer, but here's another Zen story:
Inch Time Foot Gem
A lord asked Takuan, a Zen Teacher, to suggest how he might pass the time. He felt his days very long attending his office and sitting stiffly to receive the homage of others.
Takuan wrote eight Chinese characters and gave them to the man:
Not twice this day
Inch time foot gem.
This day will not come again.
Each minute is worth a priceless gem.
The suttas tend to talk about what's "praiseworthy" rather than about what's valuable -- virtues like harmlessness, generosity, ethics, good will, discernment, right speech, wisdom.
Perhaps we should also consider as "valuable" that which is "instrumental" -- for example, a hammer is valuable (a useful or essential instrument), when you want to hit a nail.
Similarly the noble eightfold path is valuable; the Three Jewels (Buddha, Dhamma, and Sangha); or see for example AN 11.1.
The first question a native spirit once asked the Buddha:
SN10.12:2.1: “What’s a person’s best wealth?
His answer was:
SN10.12:3.1: “Faith here is a person’s best wealth.
To the second question, the Buddha once compared the chance of the gift of human life to the fate of a turtle in a vast ocean attempting to find and poke its head through a yoke with a hole throw into the ocean:
SN56.47:2.1: “That one-eyed turtle would poke its neck through the hole in that yoke sooner than a fool who has fallen to the underworld would be reborn as a human being, I say.
To the original question about value and truth, the Buddha also told that native spirit:
SN10.12:10.3: See whether anything better is found than truth, self-control, generosity, and patience.”
Human life is a rare gift. Let us use that gift well to end suffering for ourselves and others.
According to the Bhikkhu Patimokkha (quoted below), which are rules for monks, killing a human is grounds for immediate and irreversible dismissal from the monastic order (parajika).
However, deliberately killing an animal is an offense that requires only confession (pacittiya) within the monastic order, usually with the intention not to do it again. It's not as severe as killing a human.
Intentionally bringing about the death of a human being, even if it is still a fetus — whether by killing the person, arranging for an assassin to kill the person, inciting the person to die, or describing the advantages of death — is a pārājika offense. (Pr 3)
Pouring water that one knows to contain living beings — or having it poured — on grass or clay is a pācittiya offense. Pouring anything that would kill the beings into such water — or having it poured — is also a pācittiya offense. (Pc 20)
Deliberately killing an animal — or having it killed — is a pācittiya offense. (Pc 61)
Using water, or getting others to use it, knowing that it contains living beings that will die from that use, is a pācittiya offense. (Pc 62)
According to AN 6.87, there is actually a list of people a person could kill or injure, and such a person will never be able to have the right mental state or moral capacity to learn the Dhamma:
"Endowed with these six qualities, a person is incapable of alighting on the lawfulness, the rightness of skillful mental qualities even when listening to the true Dhamma. Which six?
"He has killed his mother; he has killed his father; he has killed an arahant; he has, with corrupt intent, caused the blood of a Tathagata to flow; he has caused a split in the Sangha; or he is a person of dull discernment, slow & dull-witted.
"Endowed with these six qualities, a person is capable of alighting on the lawfulness, the rightness of skillful mental qualities even while listening to the true Dhamma. Which six?
"He has not killed his mother; he has not killed his father; he has not killed an arahant; he has not, with corrupt intent, caused the blood of a Tathagata to flow; he has not caused a split in the Sangha; and he is a discerning person, not slow or dull-witted.
According to MN 86, Angulimala killed many human beings, but he could still change and become an arahant. So, probably, he did not commit the transgressions above (killing father, killing mother, killing arahant, injuring Buddha)
So this shows the value of humans above animals, and the value of the Buddha, the arahant and one's parents above all other humans.
How about a different perspective?
From Iti 100:
"There are these two kinds of gifts: a gift of material things & a gift of the Dhamma. Of the two, this is supreme: a gift of the Dhamma.
"There are these two kinds of sharing: sharing of material things & sharing of the Dhamma. Of the two, this is supreme: sharing of the Dhamma.
"There are these two kinds of assistance: assistance with material things & assistance with the Dhamma. Of the two, this is supreme: help with the Dhamma.
"There are these two kinds of mass-donations: a mass-donation of material things & a mass-donation of the Dhamma. Of the two, this is supreme: a mass-donation of the Dhamma."
This shows the value of certain kinds of gifts, sharing, assistance and mass-donations over others.
So, the Buddha certainly gave certain things more value than other things.