Will the Louvre give permission to who ever needs it to find out if the Holy Grail is in fact buried underneath the inverted pyramid?
There is a chance that Dan Brown would have seen the holy grail/sangreal documents in some form or the other. there is also a chance that the documents do exist and are buried under la pyramid inversee. However as mentioned before, there is none but a slim chance that the Louvre shall grant permission for further excavations to continue regarding this matter.
For those who do not know the facts: The Louvre got the exact location of documents as referred by Dan Brown earlier his in his book removed, so that visitors may not deface the property and try to reach the hidden chambers.
The cost of the Louvre Pyramid was 75 million francs. At today's exchange rate (1 euro = $1.3891) it cost 11.43 million euros, or $15.88 million US. the cost of the Louvre Pyramid was 75 million francs - nowadays 11.43 million euros, or 15.88 million US $ at today's exchange rate (1 euro = 1.3891 $)