It's possible, in principle, that this "transaction" was the first of its kind in Inca civilization and only happened to involve gold because that's what the Spanish wanted. But since gold is the quintessential commodity currency and has much of its value tied to others' valuing it [1], I think the burden of proof is on the claim they didn't have money. (And that's even before considering this famous anecdote -- one of only a few available, about any aspect of Inca culture.) They don't even address it though.
[1] Unlike bartered goods or services, gold (like other good currencies) is readily divisible and transportable, transfers without any skill, and stores indefinitely. Unlike many commodities, gold is not valued primarily for its functional value (food can be eaten, cloth provides warmth, etc.)
I guess you're entitled to use whatever standard of proof you want. But "random guy on the internet doesn't like it" is not the kind of thing you should expect to persuade others. For me it certainly doesn't outweigh the opinion of professional scholars.
The reason we know Romans had money is that we still have some of their money. If they did have money and you're asserting it was gold, then it should be up to you to come up with some of their golden money. There are certainly plenty of other artifacts from the era.
I get the feeling from this and your previous post that you're associating something having value with it being traded or used as money? Value and currency. Am I wrong? I know that the majority of my possessions have very little monetary value (maybe even zero) but a lot of value none the less. Judging by the small understanding of the Imca I have, they placed a lot of value in a lot of non material things and also in material things that weren't readily tradable.
A lot about the Inca isn't understood - their record keeping/message system for example, quipu. And these were made of string. A lot of their artifacts have been preserved in deserts and glaciers, allowing very fragile things to be recovered. Quite apart from first hand accounts, I would think that unless something major has been overlooked that is right in front of everyone, money didn't exist.
[1] Unlike bartered goods or services, gold (like other good currencies) is readily divisible and transportable, transfers without any skill, and stores indefinitely. Unlike many commodities, gold is not valued primarily for its functional value (food can be eaten, cloth provides warmth, etc.)