Does this cost for eurostar tickets sound about right?

Not sure what dates you are travelling on. Should be around £50 to £60 each way, maybe as low as £39 if lucky- so $63 to $75 each way. But if you are looking on the Eurostar website they must already be selling out of the lowest priced tranches. If the time of travel doesn't make a price difference it's a bit top sided but in the right ball park. Prices are not going to go down now.

Might have hoped for about $100 return, but it seems those lead in fares are gone.

So grab whatever price you are seeing.

Sounds high to me, where are you looking for these tickets, on the official website or a 3rd party? Should be closer to around $110 to $120 per round trip, standard fare...

Does that sound about the usual cost for the timing of purchase?

Looking at the eurostar site for random dates in May, that looks about right.
Prices vary by class of service and exact dates and time of trains. Prices don't go down.

What kinds of dollars are you quoting?

Thanks everyone. It is US dollars. I am using the Eurostar.com website.

Well in that case buy now.

note that the time of day often makes a difference, some trains may be much more than some others in less demand.

Are you looking around one of the May Bank Holidays? A day difference may make a big difference.

We just bought our tickets. One travel day is a Sunday and the other a Friday so maybe they are a little more expensive on those days.
Thanks again: )

Yes, Fridays and Sundays are the most expensive days (if one adds as well Monday mornings for business travelers).