Apparently over 730 million Euros have already been pledged in fundraisers for rebuilding.
Here's the big donors so far, care of wikipedia:
https://en.wikipedia.org/wiki/Notre-Dame_de_Paris_fire#Reconstruction_and_fundraising
On the night of the fire, President Macron announced that the cathedral, which is owned by the state, would be rebuilt, and launched an international fundraiser the next day.
[59][92][23][93]The exact cost to repair the cathedral is unknown, but the heritage foundation
Fondation du patrimoine estimated the damage in the hundreds of millions of
euro.
[48] European art insurers anticipate the cost to rebuild could grow as high as about €7 billion, taking into account the massive amount of scaffolding needed to replace the roof.
[94] This cost does not include damage to any of the artwork or artefacts within the cathedral; art insurers stated that any pieces on loan from other museums would have likely been insured, but the works owned by the cathedral would not have been insurable.
[94] While Macron desired to have the cathedral rebuilt in five years, architects expect the work could take up to twenty years, as any new structure would need to balance restoring the look of the original building with the structural reinforcement required for preventing a similar disaster in the future.
[95]
...
Arnault Family &
LVMH -----------Private-- France €200 million
Bettencourt Family &
L'Oréal -----Private-- France €200 million
[103]
Pinault Family &
Artémis ----------Private-- France €100 million
Total SA -------------------------------Private-- France €100 million
[104]
Paris -----------------------------------Public--- France €50 million
[105][106]
JCDecaux -----------------------------Private--France €20 million
[107]
Safra Family --------------------------Private--United States - Israel €10 million
[108]
Bouygues Family ---------------------Private--France €10 million
[109]
FIMALAC ------------------------------Private--France €10 million
[106]
Île-de-France------------------------- Public---France €10 million
[106]
Société générale--------------------- Private--France €10 million
[110]
BPCE -----------------------------------Private--France €10 millions
[110]
Kravis Family--------------------------Private--United States $10 million
[106]
Crédit agricole ------------------------Private--France €5 million
Auvergne-Rhône-Alpes -------------Public---France €2 million
[111]
Occitanie ------------------------------Public---France €1.5 million
[112]
Capgemini -----------------------------Private--France €1 million
[113]
Notre Dame University -------------Private--United States $100,000[
citation needed]
Szeged ---------------------------------Public ---Hungary €10,000
[114]