Carrying a Satellite phone on remote trips can mean the difference between life and death if things go wrong. It would be a mistake however to take further risks just because you are carrying a sat phone. In many instances they do not function and even if they do, the fact you are remote to begin with (or you would not have taken a sat phone) will mean rescue might or might not be available.
I have carried a sat phone for years. Mostly because I do many alpine objectives solo and being able to check in with the family from time to time eases tension between us regarding such exploits. However, they are no "cure all" in that regard. If you are below tree line, they likely will not function at all. If you think you are out in the open relative to the sky, but have a large wall to the south, your satellite signal can be blocked.
All that being said, $30 per month is a small price to pay for the ability to let family members know you are good. It is also nice to know if you had an accident that rendered you and/or your party incapable of extracting yourself, depending on where you amongst the terrain, you might have a chance to call for help.
Two misnomers. Satellite phones are bulky and expensive. I pay $30 US (2007) per month for an emergency plan for my sat phone. Even though my sat phones are long in the tooth and thus bulky, the newer versions are much more compact. You can buy used sat phones from your local guides as they switch to more modern phones.