so there was some truth to the statement (can't remember if it was Calonne or Necker that said it) that the French had the money but they were hiding it away in their drawers and bureaus instead of using it to boost the economy
Indeed, most of the French royal debt was held internally—not externally. Most of those which held investments in French debt in the period of the 18th century were also those who had the means to do so: this was just the wealthy bourgeoisie who were quickly growing and becoming influential (such as those who had their start in the Ferme Générale during the later period of Louis XIV's reign and the earliest periods of Louis XV's reign) but more importantly the wealthy aristocracy—the very same class seeking to protect their estate from taxation.
IMO, it was not just so much that they were seeking to defend their estate from being taxed: by Louis XVI's reign, the nobility were liable to pay
some taxes—primarily the capitulation (poll tax) established in 1695 by Louis XIV. It was repealed in 1698, but later reintroduced in 1704 and remained until the end of the Ancien Régime. The amounts were minimal: the largest payment was 2000 livres owed by the Dauphin and the Princes of the Blood; Princes and Dukes were liable to pay 1500; Knights and Officers of the
Ordre du Saint-Esprit owed 1000—this went downward from 500, 400, and 300 owed by various officials to 250, which was owed by Marquises, Counts, Viscounts, and Barons—with even smaller amounts being owed by other sectors of French society: Millers whose leases were at least 2000 livres owed 40 Livres, while physicians and surgeons in Paris owed 20 Livres. Even further down included the 3 livres levied upon physicians and surgeons in smaller towns, craftsmen of towns and villages who owed 2 Livres, down to 1 Livre—owed by common soldiers, married shepherds, various apprentices, and servants and lackeys. The capitulation was very hierarchical, but did not really demand great amounts: of France's noble families, there were perhaps 250 families who had incomes greater than 50,000 Livres and whose capitulation tax was more than 500 Livres—the majority of these 250 families resided either in Paris or at court. The second group of noble families comprised of 3500 families: these were the wealthy provincial nobility, and their annual incomes were anywhere from 10,000 Livres to 50,000 Livres—a yearly income of 10,000 Livres was considered the bare minimum for provincial luxury and most of these families were able to live lavishly in the provinces and likely paid the minimum on the capitulation tax (250 Livres)—a small sum considered. Below this group was some 7000 noble families whose incomes ranged from 4,000 Livres to 10,000 Livres which allowed for a comfortable life; some 11,000 families had incomes ranging from 1,000 Livres to 4,000 Livres—which still allowed for a fairly comfortable life if they were frugal. The last group of nobles made less than 1,000 Livres per annum—some 5,000 families were at this level: some had less than 500 Livres per annum, others had 100 or even 50. This group paid nothing towards the capitulation tax, or very little. The big issue re: the capitulation was that the nobility were able to appoint their own assessors, which allowed them the escape most of the burden (in one calculation, they escaped 7/8's of the amount due). The Clergy were also exempted in 1709 with the payment of a subsidy of 24 Million Livres. Various provinces and towns managed to gain exemptions too.
Aside from the capitulation, there was the Vingtième introduced by Louis XV—first in 1749 and again in 1756 and 1760. The Vingtième was an income tax like the Dixième levied during Louis XIV's reign, and was meant to collect one-twentieth of everyone's annual income, and was to be collected directly by the government. Like the above tax, the First and Second Estates were able to purchase exemptions through a payment of the
Don Gratiut to the crown (essentially a free gift, or lump sum payment). Two other Vingtièmes were levied during the Seven Years War: the last was abolished, but the first two remained. Much like the capitulation, there was wrangling over how it the tax might be collected and how it would be assessed: Bertin, Louis XV's Controller-General sought land surveys, but the Parlements resisted this idea, and Bertin was later sacked. When Laverdy succeeded him, the Paris Parlement agreed that the tax could be levied, but it would be based on old property assessments, meaning that the income of the tax wouldn't grow as the national income did. Maupeou and Terray attempted to make improvements, but the Vingtième largely remained inefficient. Calonne abolished it in 1786 to replace it with new taxes, but the controversy and his fall from office meant that nothing was accomplished. Brienne eventually settled matters and had the Second Vingtième extended in 1787 (unlike the first, it was regularly extended through the 1760s-1780s), and it remained until 1790.
The primary issue with these taxes were:
a) Their collection was extremely inefficient
b) They had baked in exemptions or had loop-holes to allow the First and Second Estates to become exempt; those that could exempt themselves did
c) Proper assessment was almost impossible: for the nobility, the amounts their paid were sometimes laughably miniscule compared to their incomes
d) Put even further burdens upon the Third Estate, already liable for various other taxes