Sacrifice?
I never thought of it as a "sacrifice" when I joined the Corps. I did it because I thought I'd be good at it (I was), that I'd enjoy it (for the most part, I did), and because it offered adventures that I couldn't find in ND (that puts it mildly).
So here's what I see as the general range of sacrifices:
Some die in the line of duty, some die in training (seriously, this was a big issue), and of course there are those with PTSD and debilitating injuries, and last but not least...the time away from home and family (often leading to divorce or at least fractured relationships). These are the personal costs of joining the service. There's also the professional/career time lost in a trade/profession that usually pays better. Even if you get out after a 4-6 year stint and have to re-invent yourself, many remain a step or two behind their age group in professional development and earnings.
These opportunity costs and the risk for potential for life-long health issues, or even death, are rarely considered by those who join. My theory on this is that when you are willing to join, the classic "that can't happen to me" mentality rules the day.
What I received for those "sacrifices" is a thorough grasp of what it means to be an American. The rights, privileges, and responsibilities of my citizenship have been forever incorporated into who I am, and is something I try to help friends and family understand. I've had to work harder, and will likely work longer, all just to catch up to my contemporaries to obtain the same level of financial goals.
I wouldn't trade my lot in life for all the tea in China.
In short, I like to think we all did it simply because we wanted to.
Allen (USMC 1988-92)