I think an MBA is a longterm investment. As such, it comes with risks.
While trying to weigh the value of the investment, you might want to ask; what is the worst thing that could happen, if you do an MBA.
I am guessing that for many, the worst scenario is to be unable to find a job after graduation. No one would want to be jobless with a huge student debt. Tepper's latest (Class of 2010) job placement stats are encouraging: the rate of job acceptance after 3 months is87 % (88 for American students and 84 for internationals). Still, everyone and every year are different.
If you can accept the risks, whether it is remaining jobless or remaining at the same salary level, MBA can offer much more than just a prompt promotion or fast track to the chair of CEO; it is an opportunity to network with diverse people, experience the new home town, and make memorable 2 years and beyond.
This may sound luxurious. I agree. Regardless of the program, the capacity of doing MBA is an luxurious option from any standard. That's why the schools search for people who have the greatest potentials to give back to the societies, companies, communities etc., what the students are getting during the next two years.