Princess Caroline alone is not worth much, only through her brother and husband can she claim vast personal wealth. The Grimaldi Family alone are worth around US$2 billion and the Prince of Hanover is said to be a billionaire, but I do not see any real evidence to support this.
It was my understanding that Caroline and Albert inherited approximately £1.5 billion from their father. Ranier was unhappy with the way Stephanie was leading her life rewrote his will in 2001 and left her roughly £12 million. Albert has apparently been quite generous with Stephanie although I am not certain why she needs it. Several articles attest to this including the tabloidy DM. http://www.dailymail.co.uk/news/article-4588/spike-Stephanies-inheritance-slashed.html
The Grimaldis also control much of the gambling income in Monaco which earns them a lot. One has to remember it is a shady place and I am certain they have A LOT of untraceable wealth, like gold bullion.
Caroline also inherited around 200 million when her second husband, Stefano Casiraghi died in 1990. Caroline's children stand to inherit some of the vast Casiraghi landholdings in Italy. (On Charlotte's fifth birthday, Stefano's parents reportedly gave her an island off the Italian coast valued at about $7 million.) Prince Ernst-August is worth approx $140million with $100 million of that, properties.
From the Telegraph http://www.telegraph.co.uk/news/worldnews/europe/monaco/1487329/Tears-in-Monaco-after-passing-of-Europes-longest-serving-monarch.html
The bulk of his fortune, unofficially estimated at up to £1.5 billion, will be divided between Albert and Caroline.
Concern about some of the company Stephanie kept led her father to limit her direct inheritance, according to the American biographer J Randy Taraborrelli.
On his assessment, she would still be left with a monthly allowance of more than £30,000, properties in France, Switzerland and the US, and the prospect of greater control of her share should she be deemed capable of handling it maturely.
Many estimate Ranier's estate to have been approx. £2 billion, with 75% of it real estate.
Dozens of international banks do business in Monaco and VIE for the opportunity to do businees in Monaco *, and pay the Grimaldis, who own most of Monaco and its chief holding company, the SBM, many many millions per year. *The russians built Pr. Albert a dacha as a "gift", either for favors/payback from is IOC/Olympic committee votes another Russian wanted to open a bank and presented him with equally outrageous "gifts".
Their cousin,Christian De Massy, son of Ranier's sister wrote this book Palace: My Life in the Royal Family of Monaco, in which he claimed the annual income of the Ranier's was
Quote from wikepedia "Prince Albert is one of the wealthiest Royals in the World valued at more than $1 billion, this include vast a mounts of land both in Monaco and France, and which include the Princes Palace. His wealth does not include other members of the House of Grimaldi which are valued total at over $1.5 billion." FORBES magazine also estimates that the Grimaldis are amongst the richest Royals in the world. They are behind several Arab princes/Sheiks and the House of Lichenstein, with the latter worth $5 billion.
Any way you slice it, Princess Caroline inherited at least £750 million from her father TAX FREE, £140 million from Stephano in total close to £1 billion. Factor into that the fact that she earns tens of millions a year in interest. She also inherited the vast majority of her grandmother Princess Charlotte's jewelry.