From Wikipedia –
In all the French spent 1.3 billion livres to support the Americans directly, in addition to the money it spent fighting Britain on land and sea outside the U.S.
France's status as a great modern power was affirmed by the war, but it was detrimental to the country’s finances. Even though France's European territories were not affected, victory in a war against Britain with battles like the decisive siege of Yorktown in 1781 had a large financial cost which severely degraded fragile finances and increased the national debt. France gained little except that it weakened its main strategic enemy and gained a new, fast-growing ally that could become a welcome trading partner. However, the trade never materialized, and in 1793 the U.S. proclaimed its neutrality in the war between Britain and France.
Most historians argue that France primarily sought revenge against Britain for the loss of territory in America in the Treaty of Paris. However, Dull, in 1975, argued that France intervened because of dispassionate calculation, not because of Anglophobia or a desire to avenge the loss of Canada.
It was just another contributing factor that led up to the French Revolution so it's worth researching the causes of that as well. Ironic that France in trying to weaken her old enemy Britain actually contributed to the downfall of her own monarchy.