With the signing of Treaty of Pressburg, Andrew Roberts explains (in Napoleon: A Life), the Austrian Emperor lost 2.5 million subjects and one-sixth of his revenues, making a lasting peace unlikely:
When Vivant Denon presented Napoleon with a series of gold medals commemorating Austerlitz, one of which showed the French eagle holding the British lion in its talons, Napoleon threw it ‘with violence to the end of the chamber’, saying: ‘Vile flatterer! How dare you say the French eagle stifles the English lion? I cannot launch upon the sea a single petty fishing boat but she’s captured by the English. In reality it’s the lion that stifles the French eagle. Cast the medal into the foundry, and never bring me another!’
He told Denon to melt down the other Austerlitz medals, too, and come up with a far less grandiose design, which Denon did (it had Francis and Frederick William’s heads on the reverse). There was a modicum of modesty still left in Napoleon in 1805; he also turned down Kellermann’s proposal for a permanent monument to his glory and had David destroy an over-flattering gilt model of him.
[…]
A report from the Grande Armée’s receiver-general in January 1806 showed just how profitable the victory at Austerlitz had been for France.25 Some 18 million francs had been collected from Swabia as well as the 40 million francs demanded from Austria by the Pressburg treaty. British merchandise was seized and sold across all the newly conquered territories. In all, revenue amounted to about 75 million francs, which, after deducting costs and French debts to the German states, left France nearly 50 million francs in profit.
[…]
War must pay for war,’ Napoleon was to write to both Joseph and Soult on July 14, 1810. He used three methods in a bid to achieve this end: straightforward seizure of cash and property from enemies (known as ‘ordinary contributions’); payments from enemy treasuries agreed in peace treaties (‘extraordinary contributions’), and the billeting and maintenance of French troops at foreign or allies’ expense.
[…]
Ordinary and extraordinary contributions produced 35 million francs in the War of the Third Coalition, 253 million francs in the War of the Fourth Coalition, 90 million francs of requisitions in kind from Prussia in 1807, 79 million francs from Austria in 1809, a huge 350 million francs from Spain between 1808 and 1813, 308 million francs from Italy, 10 million francs in goods seized from Holland in 1810 and a special ‘contribution’ from Hamburg of 10 million francs the same year.29 The savings made by the use of allied military contingents (253 million francs) and by despatching French troops to be billeted on satellite states (129 million francs), as well as a total of 807 million francs in ‘ordinary contributions’ and 607 million francs in ‘extraordinary contributions’ over more than a decade brought in a total of nearly 1.8 billion francs.
Yet still it wasn’t enough, because between the breakdown of Amiens and 1814 no less than 3 billion francs was required to finance Napoleon’s campaigns.
[…]
So the war did not pay for the war, but only for 60 per cent of it, with the remaining 40 per cent being picked up by the French people in various other ways. Yet these did not include the imposition of direct taxes on Napoleon’s strongest supporters – French tradesmen, merchants, professionals and the peasantry – except for the discretionary taxes on drinkers and smokers. Nor did it involve any direct taxes on middle- and upper-class incomes, even though Britain levied income tax at 10 per cent on all incomes over £200 per annum, an unheard-of imposition at the time.