No, I'm quite serious. They're the Four, not Tzeentch and pals, and dhar isn't the only temptation we'll encounter.
Mathilde isn't a raging murderer or some weird disease cultist (how do people even get tempted by doom-Shrek?), and she's pretty well indoctrinated against the temptations of chaotic magic (in a good way), and being proud and liking trashy romance novels aren't evil character traits on their own, but exaggerating those desires to such obscene proportions (more than multiple years worth of the entire income of province-wide institutions!) is pretty much a textbook case of going way too far.
See, this kind of thing is the reason I stepped away from SV. This inability to consider things within the context of a character, and projecting your own biases, assumptions and outlook onto a character that doesn't share them. It's worse than annoying; it's
disappointing.
But, nevertheless, let me explain something important. Money has value as perceived by society. Money has value as perceived by its holder. These are not quite the same thing. How much 100g is, whether it be a day's wages or a fortune, doesn't actually matter. What matters is how much Mathilde feels it's worth to her.
Mathilde possesses money, but Mathilde does not consider herself wealthy. This is because Mathilde has taken a vow of poverty, and doesn't consider the money hers. Not
really hers. She decides how to spend it, sure, but it's not hers for keeps. It exists to further her duties and maintain her person through assorted means. This diminishes it's perceived value - when you purchase something with money that isn't yours, you are experiencing a net gain, because the thing you buy
is yours.
And despite her remarkable ability to accumulate wealth, she steadfastly considers money worth only what it purchases, for this very reason! Holding money in abeyance is good, in the sense that you can cover unexpected expenses, but money that is unspent is money that isn't doing its job. Money is for spending. And Mathilde currently possesses more money than she knows what to do with, further diminishing its worth to her because there is no
shortage. So what does 100 gold mean to her? Nothing.
So, when you talk about how much 100 gold is, you're missing the point. Mathilde isn't trading
her gold for anything, she's trading Dawongr Weber's too-plentiful gold for a tangible luxury that she's actually allowed to fully own, no loopholes needed. This has various justifications; she can enjoy them, she can use them for social purposes, she can build furniture out of them. What it's not is
obsession, because, sure, romance novels > gold to Mathilde, but this is because gold has low value, not because romance novels have unreasonably high value.
Now, comparing the expenditure to what it could otherwise buy, such as another room for the tower, and you see how it's an inefficient purchase, but given that there is so much money, it's hard to consider it worth arguing about. Mathilde literally has more money than she knows how to spend.