Inexperienced travelers find that taxing. 10 hour flight to Europe, a few days to acclimatize, then the cruise, then fly back to the states and then take a few days to re-acclimate...and if you dont have the time to take the extra days to acclimatize, it can be quite tiring. Either way, it can be a lot for some people.

And yes, there can also be monetary costs as well that are a lot for some people.