Five axis for 5 pounds? Link please :-)
Depends on what capabilities you need for what you want to do.
Remember, the BoB is just a card for connecting the wires (sensors) between the machine and the Controls.
What do you want to do/make.
What Controller will you use?
Think about needed/desired control and sensing functions such as:
Motors (you mentioned 5)
Sensors - home for all axes, how about limit switches for these axes - do you need + and - sensing; can the home be used as limit in your situation and are they independant or wired in a series or parallel fashion?
Controlling motors, spindles, pumps (cooling, mist, vacuum table(s) or other), even a light on the spindle head can be useful
E-Stop is one not to omit!
Do you want to add anything else in future - allow for expansion. If you haven't had/used a machine before, you soon realise a "widgety thingy for what you do" might be nice :-)