Hi all,
I am just checking any trains apart from Eurostar to travel between Paris to Amsterdam, Amsterdam to Antwerp, & Antwerp to Paris? Eurostar is very costly for my dates.

Thank you

For searching for my own trip next month I found that thetrainline.com offered various choices those routes including the bus.

Yes, there are other options - I know that there is a Dutch IC commuter train between Amsterdam and Brussels, with a stop in Antwerp, and 2 other options from Paris to Brussels (TGV InOUI, and Ouigo, the second of which is cheaper). Eurostar is what I would think of as a premium rail service. I recommend you use the national carrier websites like b-europe.com or nsinternational.com to buy your tickets because they don't carry extra fees unlike third party websites. However if you are really on a budget, I agree that perhaps Flixbus or car sharing like Bla Bla Car might be more helpful for you.

Lavandula

You can check rome2rio.com -- just be sure to click through to the underlying sites and check for the days you plan to travel.

Look at Seat61 website. All the information on trains you will ever need.

Plenty of IC trains from Amsterdam to Antwerp. Prices depend on when you are going and time of day, but around €25 one way on NS International's website. Some you have to change trains 2 or three times, others one change at Schiphol, always really easy and adjacent platforms.

Have a look at Belgian railways website too.

As mentioned by Lavandula, there’s a slower and much cheaper way to travel from Paris to Antwerp without taking Eurostar.
You can take the OUIGO Train Classique from Paris to Brussels, which runs on the conventional (non-high-speed) line.
Once you arrive at Brussels-Midi, you can simply hop on a regular Belgian domestic train (SNCB) to Antwerp.