Here’s why I don’t think it’s just hyperbole: this isn’t the only place where Littlefinger and tenfold increases comes up.

 In A Storm of Swords, Tyrion states that while “crown incomes are ten times higher than they were under Aerys… [so] are the crown’s expenses.  Robert was as generous with his coin as he was with his cock… the incomes are considerable, but they are barely sufficient to cover the usury on Littlefinger’s loans.”

As I explain in my essay, this claim on its own is suspect, because if incomes have grown by tenfold (highly unlikely on its own) and so have expenditures (likewise highly unlikely), then debt-to-income shouldn’t have grown, but somehow a tenfold increase in income is only sufficient to cover the interest rate, let alone the principal of the loan. 

To me, this makes Littlefinger’s claims from Gulltown part of a pattern of behavior, where he makes extravagant claims of increased income, and then takes on much larger levels of debt than would be necessary to meet expenditures. (For example, his practice of not paying back any principal on the debt and taking out new loans to pay the interest, which is accounting malpractice likely covering up fraud.)