Please help to confirm which days is the best time to visit Versailles

Versailles is always busy. There is some overlap in your researched "best time", so why don't you go with Thursday?

Crystal ball??? Even if RS or Google is right on their averages, one individual's one-off experience is not to be equated as equaling the average experience of the population visiting Versailles. Statistics are not perfect predications of individual experience.

Go when convenient for the rest of your itinerary and be prepared for crowds whenever you go.

Maybe sometime in the winter when it's not so crowded? We made the mistake of going to Versailles and vowed never to subject ourselves to an experience like that again -- way too many people packed into one place. I would have been happy to have a picnic and walk around the grounds however.

I hear there are other castles and chateaus to visit that aren't nearly as crowded. Check this out:
https://www.youtube.com/watch?v=MAbI8Q-WRXg

Even though you need a timed ticket to visit the Palace, any day in high season is going to be very crowded. Any day in shoulder season will just be crowded. You could get lucky if you are going off season. Picking one day of the week vs another? Flip a coin.

RS travel book mentions that late spring and fall usually brings the biggest crowds. I will be going there in October. Summer might be dead because of high heat. No one wants to travel in very hot weather.

Versailles ticket is costly - Eur$61,90.
https://www.versaillespalace-tickets.org/en
Is it scam or not, I wonder?

Is it Versailles' official ticket? I read that RS travel book states only Eur$19.50 (Chateau only).
https://en.chateauversailles.fr/
It reflects the same price in RS travel book.

May I check that the visitors are requested to drop off their bags before entering the Chateau and must retrieve it one hour before closing. What i meant is, we have to do sightseeing inside the Chateau without our own bags till we exit from that Chateau, then we retrieve our bags back?

J@p28al,
The price of 61.90 euro is not from the official sight. High season price for the whole shebang is 32 euro and 24 euro in low season. The website you mention, en.chateauversailles.fr, is the official and correct one to order tickets. Versailles will always be busy, especially in the summer and on weekends, IMHO. You can't guarantee that a particular Wednesday or Thursday will be crowd-free. That being said, it is worth a visit, at least for one time. I have been twice and am glad I went. It is quite a bit over and above other typical palaces....not my favorite, however. Do go if you can. Just reserve your time for as early as possible, 9:00 a.m. Plan on several hours in case you want to walk on the grounds to the Hameau de la Reine, the Grand Trianon and the Petit Trianon. They are quite large. I did it when I was 30 but couldn't do it now at 81, or even at 71.
By the way, I believe entrance is free for those under 18, but a reserved time is still required.

This is the official Versailles website:
https://en.chateauversailles.fr/
When you're looking for tickets for places like this, Google "official xxx website" and don't fall for a third-party vendor.

Thanks a lot for your tips and advice.