Thanks for the information. I am interested in one way trip. My travel date (12/30) is not flexiable. The only one way fare I saw for that day is 94 euro on thalys.com or 89 USD on travellerspoint.com. So I thought purchase in US might be a good option at this time.

I did check the last minute special section of thalys.com. It looks like in order to take advantage of that deal I will have to wait till 12/27. Is there a risk that there will be no tickets available by then?