We're actually leaving tomorrow for AMA Europe Heartland Cruise (first 1/2 is very similar to PARIS).

A cab will run approximately 40 Euros. If people are in couples, cab would be cheaper than the AMA transfer. We're taking a cab.

Train and Bus (operated by Air France and drops you off by the Opera - cost is something like 17 Euros per person) are possible alternatives. Although I don't really suggest them since you're all travelling with bags and you'd have to take a cab upon arrival in the city.

Train can be a bit risky with all the pickpockets in Paris (beware in general), I have a Flyertalk friend who had his laptop bag (along with his passport) stolen on the train in from CDG.

By the way, I believe that AMA is now using the Crowne Plaza on Rue Republique as the host hotel now (since the Paris Hilton has closed). We've got to get ourselves over there on Mon for the transfer to Trier. We're staying at the Park Hyatt (booked in a suite) on points since the Crowne Plaza's effective rate through AMA is $500 a night.