So, fair warning here, this will all be anecdotal evidence. I will site no figures because honestly if you are debating graduate school the figures don't mean a thing.
Why should you go to graduate school?
If you have a limited social life and want to spend much of your time doing work you should go.
If you live to work in your field, go.
If you have to get a graduate degree to get the job that you know without a doubt that you need, go
If you have a company paying for you to go, stop reading and go.
Why shouldn't you go?
If you found undergrad easy, and that is your only reason.
If you don't like long hours and weeks don't go.
If you are looking for a nine to five experience don't go.
If you don't know what you want to do with the degree afterwards, don't go. Figure out the barest hint of a plan first.
A good portion of graduate students don't finish at all. Many programs will accept anyone just so they can account for the drops. So if you get in and want to get out, don't feel bad. Instead if you want to get out, take a chill pill, talk to people around you to make sure you aren't jumping the gun and then quit.
A good portion of graduate degree holders don't get the jobs they are looking for. That doesn't mean they work in a Starbucks, it means that they aim for jobs which are ultimately unattainable due to limited positions. There are only so many tenure track positions. So while there is no harm in going big, working yourself to the bone for a tenure track position, don't expect immediate success and keep a look out for other things. The same goes for a lecturer position, aim for it but avoid tunnel vision.
You will work hard. It cannot be stated how hard you will work for seemingly little or actually little appreciation and gain. Though people will eventually respect your work if it is good. You will lose sleep and you will look at peers that have normal jobs and feel envious quite a bit. It's normal.
You might not earn that much more or you may earn a whole lot more. There isn't a pot of gold at the end of this rainbow. If you get the position you want you may get lucky and it'll pay 6 digits. But remember that PhDs are getting more plentiful and you may not get the position you want. This all depends on your specialization and skillset. Make sure you investigate your field.
Yeah, that's it. Just another opinion out there.