I have read that it is more economical to purchase a same day round trip ticket than purchase a one way ticket. This was confirmed by checking prices on the Eurostar web site. It looks like it is common practice to purchase the round trip for one-way travel and discard the return ticket.

Are there any baggage restrictions if we purchase a same day round trip? We would each be bringing at least two pieces of luggage on the same day round trip.

Also, it says that if you pick up your ticket in Paris, you need to use a French credit card. Does this mean you can't use the credit card you purchased the tickets with? (Chase Bank Visa)

Your comments will be greatly appreciated.

You can take as much luggage as you can carry and get on the train by yourself.

As for the credit card - US credit cards won't work in many ticket machines (they don't have an imbedded chip) But you can always take your credit card to a manned ticket window to get you tickets. Just be sure to leave plenty of time in case there is a long line (or pick up the tix a day or two ahead of time)

You're correct about return trip cheaper than one-say.

Eurostar has the same luggage restriction regardless of the types of tickets. You can bring two pieces on-board (stored at the end of each train cars).
I believe there is left luggage service at Gare du Nord.

Day returns can be extremely hard to book on some days and often only on the very earliest trains. $94 in US - do you get a better price online in Europe? If not why bother picking up ticket there at higher price - lower price yes but i think Raileurope's $94 day return in hard to beat. Actually there is a cheaper $90 one way fare thru RailEurope Mon-Thu and you can probably book a train later than the usual 7am trains available on day returns. So it's not always more economical to do the day return - only on Fri, Sat and suns is it. If you're under 26 you can get one ways as low as $45. 60 and over there is a $90 senior fare one way - this is a better fare because it can be changed once in Europe up until the time of the train.
But Raileurope charges a $15 booking fee per order and a $15 mailing fee as your order would be under $200 - i always recommend BETS (800-441-2387) for their Eurostar expertise and won't charge the $15 nmailing fee - Raileurope also charges $25 for phone orders in case you want to talk to someone - BETS doesn't.

Thanks you for your helpful responses!

Raileurope raised or readjusted prices, in some cases lowering them, last week. The day return price is now $96 and the e-mail from Raileurope also says that Eurostar is increasing the 'bucket' of seats allocated to this fare so it may be easier to book than before.

Keep in mind that Day Return tickets in effect are often only bookable on the very earliest trains of the day - as bona fide day returners would want to do. And these should be reserved far in advance to get them.

If you look at the Eurostar website you'll see that there are several types of return ticket for the same fare as a day return.

There's even more choice if you clear out the cookies and go into the Eurostar website pretending to be British / Belgian / French...

this used to be true in the U.S. as well, in fact the $90 return fare, requiring a one day stay at least, was cheaper than the $94 day return - but it was valid only Mon-Thu trains 11am-3pm.
Now Raileurope's cheapest return is $140 with no day restrictions but harder than hell to book on many weekends.
So it may pay to go to the Eurostar U.K. web site for cheaper returns i guess.

Boy those last trains between London and Paris must be nearly empty with everybody buying one day returns and not using the return!

Incidentally you can book Eurostar Paris-London-Paris on the Eurostar UK site and not have to worry about the French SNCF site...

This past summer I bought a same day return (eating the return) for 40 quid somewhat less than $80 (the pound has not quite gotten to $2 US) on the Eurostar UK site (at the start indicate you're from the UK and so you don't get a cookie directing you to a US subsidiary of Eurostar) and unlike the crooks at Rail Europe do not charge you $15 to ship the tickets, they post them, even to the United States, for free!

Last summer we used a round-trip EuroStar fare for just one way from London to Paris, throwing away the return ticket. It was cheaper than getting a one-way fare. But we didn't need to buy the return trip for the same day. Unless things have changed, you can pick any day to return that gives you the fare you want. We bought it through BudgetEuropeTravel.com, because I wanted to be sure I was getting it right. They charge a very minimal fee, and are current with the latest restrictions. They said last summer that it wouldn't be long before EuroStar started charging a penalty if return tickets aren't used, but keeping your Visa number on file and dinging it with a penalty fee.

<unlike the crooks at Rail Europe do not charge you $15 to ship the tickets>

xyz123 - if you going to give advice be sure you have it right - RailEurope charges no shipping fee on orders of $200 or higher - zilch. Nearly all Eurostar orders would be over $200 in cost.
For the past three years until a few weeks ago those crooks at RailEurope were selling fares that were rarely as low on UK or French Eurostar web sites - $90 returns for example for three years - now with their increase no longer true - but for three years i guess those crooks at eurostar.co.uk were gouging as well.
You forgot to mention the $15 booking fee RailEurope charges for which you could legitimately criticize them.

Somebody pointed out the $15 fee for shipping and I just followede up on it but same difference $15...

I have always done better by booking directly with Eurostar in the UK...as I said I paid less than $80 for a same day return this past summer by booking directly with Eurostar in London, far under the $200 which means I would have paid $30 to the crooks at Rail Europe.

My other point with Rail Europe and I won't characterize this as crooked you don't deal with them in real time...you make a reservation they then often time tell you what you booked is unavailable...now maybe that has changed in the past couple of years but about two or three years ago I tried to book a Thalys special they were advertising from Amsterdam to Paris which did undercut the posted Thalys fare (even with the extra $15 for shipping) and booked it only to receive an e mail that what I booked was not available and offering me a higher priced ticket.

I just don't like doing business that way.

that's a valid criticize in real time now - their web site gives a price for a specific train then when you come to book it yes often a different price - not always higher but often and whether this is programmed crookedness or not i don't know - i'd say more incompetence but it still happens with point to point tickets. And they do not show all available trains that they can actually book.
But crooked i don't think is the word or just about every business enterprise who is trying to maximize profit could be called crooked. And as of a few months ago point-point tickets as RailEurope points out can vary in price daily so maybe it is the processing time - things are apparently now priced in euros and not dollars as was always the case.

You've got the internet, it takes about 5 minutes to compare prices between different conpanies, so what's the problem?

exactly - the point was crookedness and i believe like you say just compare and take the best and most convenient deal. I don't believe it's crooked to have higher prices - let the buyer compare and see!