Yes, it is more like an effective trading activity with a money system is necessary to have the resources that a great king needs to suck blood from.
That's essentially Graeber's argument: commodity money (coins) was introduced by the state as a means to get stuff from the people (mainly to pay armies with), and commodity money in the form of coins didn't emerge from the market (apart some examples that were not the basis for the large usage of coins in empires). Peaceful free markets seemed to prefer credit money, and commodity money on large scales always was introduced by states (with big armies).
Any market, and markets will pop up everywhere, will have some good that is durable, compared to the other goods, divisable, compact etc, the money traits, and that will be preferred as a value holder to the next market. The money value could be small compared to the use value, but due to that commodity's liquidity, it will be non zero. That is really all that Adam Smith proposed. As markets develop, get larger and more global, at some point gold will be included, and that commodity has the best qualities. Bars, where you could cut off a length, is again a later development, then coins, which can be seen as a standardized size. The picture of kings could be seen as a quality stamp (but maybe it also was a marketing scheme for the king).
That is exactly the story that Graeber claims is not the slightest bit of historical proof for (except in international trade). His point is that free markets, left alone by a state, develop credit money, of which there are plenty of historical examples, and that not a single historical case can be illustrated with the above process where on large scale, bartering happened, and from that, an intermediate good evolved that turned out to be gold (again, except international trade).
This isn't really rocket science, so why does Graeber and others have so much problems with it? For one, I think he is an apologist for the state, and can't really envision anything civilized without it.
No, Graeber is an anarchist. His point is exactly that commodity money is introduced by states to oppress the people and to go to war with. He claims that more advanced non-state commercial relations are based on credit, and not on exchange of intermediate goods.
I have to say I also believed the standard story, and I still think it has its value as a gedanken experiment in a trustless environment. But I think that the important message from Graeber is that there is a second, much more obvious, solution to the "implausibility of the direct barter difficulty" and that is credit. And for some or other reason, this has been left out from the economic tale - although when you think about it, credit money is all around us ! In fact, the rarity is commodity money.
Now, there are illustrations of the emergence of commodity money, as you said yourself. There are also the famous cigarettes in prison. So that doesn't mean that the standard mechanism doesn't apply. But, after reading Graeber's book, I come home with two things I didn't realize before:
1) credit money is also a solution to the puzzle of implausible direct exchange, one for which there are tons of historical evidence
2) the particular case of gold emerging as the preferred commodity money in the normal daily commercial markets has not the slightest bit of historical evidence. Gold seems to play a role between kings, temples and in international trade, and the only actual historical records for introducing gold in commercial relationships apart from international trade come from states issuing coins, or from looting soldiers. And not - that's Graeber's thesis - from a gradual preference of the market.
Now, not being a historian, it might very well be that Graeber tells us an erroneous story, but then I would guess that the market emergence of gold as the preferred commodity money in daily economic affairs is well illustrated historically - of which Graeber claims, no single bit of proof exists (that bartering turned into bartering pieces of gold, and in the end, that gold coins were calbrated pieces of gold to barter with).
