I own one that I use for my business. You need to be on deck with clear lines up to the satellites.
As for cost.... cough cough. If I had to pay the bill out of personal money rather than the business, I would probably just send a post card
The sat phones get very expensive, but they simply cannot be beat when you are (literally) in the middle of nowhere and need to make contact with the world.
The phone works in the middle of the desert, in the jungle, on top of a mountain or the middle of the ocean. Can be a real lifesaver, but if you are taking it just to "stay in touch" while on the cruise, don't go through the expense. Whatever it is, it can wait till you get back.
And if it is something really important, the people that need to be able to reach you in an emergency should have the contact information to reach you on board.
If you are sailing with me on the Victory on June 26, look for me and you can use my phone