I
guess you could see it that way, but it's just logical extrapolation from Canon clues. Of the grand total of
4 vaults we see in Canon (I
think it's just 4, but I could be wrong), two, Harry's and Bellatrix's, are absolutely stuffed to the brim with Galleons. The other two are apparently anomalies since one is the vault where Hagrid picks up the Philosopher's Stone, and the other is the Weasley vault. The Stone's vault was almost completely empty if I remember correctly, just a package wrapped in brown paper laying on the ground in the middle of it. So that was likely a temporary transfer vault set up for a trusted person to get the Stone. As for the other one, well the Weasley's are consistently noted to be
exceptionally poor comparatively to almost all other Wizarding families. They aren't in poverty, but they are pretty much the only family noted to be using second hand items like clothes. Everyone else is from a pretty well off family, and if the family lines are so exceptionally long that accumulation of wealth wouldn't ever really stop would it? Like I said compound interest is a thing. Even if it just sits in the account for decades or centuries, it'd start to add up pretty fast wouldn't it.
So I mean yes technically those are all assumptions, but only because Rowling didn't do exceptional World-building and left rather large holes that others have to fill. Still it all depends on how
@Fencer wants to play it in this Fic, so this could be an entirely moot discussion. Regardless Taylor and Harry are obscenely rich due to Harry inheriting the Black vaults from Sirius, I'm
pretty sure that fact is 100% Canon.