That doesn't ring quite true to me. We've many times discriminated as not qualities things which manifest cambridge change. An "externally grounded quality" such as financial value is exactly the sort of thing that can change without there being anything about the bearer changing, vice price of gold.
It is the case that financial value can *also* change because the bearer changes, such as when the value a fruit goes down if it gets bruised or old.
So, before even the question of quality version realizable comes up, it seems that the dependencies of something like financial value should be accounted for. BFO has relational qualities which is a starting point. I have argued in the past that most dependents have relational cases. But, in the case of say dispositions, the other dependency can land up, in current BFO, being masked by being wrapped up in the condition/trigger for the disposition, something we don't have an explicit representation for.
So let's say that financial value depends on both an entity that is perceived as having the value, and the entity which sets that value. I see some different cases. It can be the case that there is an interested buyer and an object that has value to that buyer, and in that case the two dependencies are clear. In other cases it is diffuse, a result of the "market", or the even more diffuse "society". One view is that those things are aggregates/populations at least, so there is a potential target for the dependency. Even in the absence of categories for the relational cases, we can still record the dependencies with the s-depends relation.
To the question of whether "financial value" is quality or realizable, I'm with you that it falls most clearly in the realizable bucket. That said, I think it's hard for practicing ontologists, in many cases, to make the distinction. Take the classic example of "quality" color. There's no color if there isn't a process in which light shines on the object, sensors register light and some process classifies the measured spectrum of the reflected light. So is color a realizable? I'd say so. The quality is reflectance, which is a property of the material.
What to do about this? I'm honestly not sure. I try to make the distinction and think I can make it reasonably well, but often enough my judgement on these things does not make it into an ontology. I think, at least in some quarters, that the distinction between qualities and realizables is considered more trouble than it's worth. So in practice maybe things land in the realizable bucket when it's considered that the manifestation is relevant in the domain. The unfortunate thing about that is that a judgment of relevance isn't objectively reproducible, which harms interoperability, which depends on systems in which judgements are reproducible.
As an aside, I've had conversations about exactly these issues with Barry as he's worked toward a definition of capability.