Frecciarossa high speed train - Milan to Paris

If those prices are from Trenitalia that is probably correct.

Where are you searching?

I have looked at both Rail Europe and Trainline.

First off -- Rail Europe and Trainline are travel agencies. They do no operate any trains anywhere. You should stick with the actual train site - Trenitalia - for tickets. However a fare of 45 euro for a discounted tickets is correct although it will vary a bit depending on the time the train departs.

October 4, 2023

Just checked Oct 4, some fares as low as 35 euro. Although there is a disclaimer that the final fare could be adjusted because it involves the french train system. Need to go through to the final payment but it looks like a good deal.

There are basically two companies operating on that route: SNCF and Trenitalia. Trenitalia is faster and has the nicer trains in my opionon. Trainline is useful here as they show the prices of both services, as well as options that route you via Switzerland.

October 4, 2023

On the 4th of October, the 2 direct trains run by Trenitalia that depart from Milano Centrale and call at Paris Gare de Lyon cost 35 € per person not 50. These two Freccia high speed trains depart to Paris at 6:25 AM and at 15:53.

The EC trains run by Trenitalia and SBB cost € 42 from Milan to Basel. Once in Basel you'll have to pay for the TGV French train to Paris Gare de Lyon.

While trainline can more or less be trusted to book direct trains once you know you are paying more to get nothing more, on tripadvisor there are pages of complains about RailEurope.

Try here for pricing
https://www.bahn.com/en

Thank you all for the information. I will follow up with all the sights you recommended.
I appreciate your assistance and knowledge. Cheers!