Having actually gone through military boot camp, it isn't an experience that I would be willing to repeat. Then again, the point of that boot camp isn't solely for fitness.
Group boot camp classes , depending on the individual, might work better than a solo routine or one on one with a trainer. The atmosphere generated is one of shared experience, of pain and triumph. In such group classes, sometimes you rely on your classmates to motivate you to keep going, and in turn do the same for them. Personally I wouldn't pay for such a class, but then I have no exercise regiment that I am dedicated to at the moment.
As with anything, you get back what you put into it, and so time and money is up to the person interested in that experience. Cost may be a factor, but quality is always what you want to find, and sometimes that requires paying a little more. Obviously, if the more expensive option is going to be detrimental to your financial security, you might want to seek out a cheaper option, but that choice is entirely up to you.