In america, nothing really. In america wal mart is usually cheaper than the BX anyways. Overseas however things like jeans a much more expensive out in town so people buy a bunch at the BX to sell to locals, for example. OSI and military police investigate this type of thing and will get you.
- - - Updated - - -
Where is this information located?
You sign piece of paper at your time of purchase where they tell you this information. I bought my Mossberg 930SPX from the PX at Benning.

