For extra areas of lipo during a BBL, are the arms and thighs considered to be one area or separate?

Liposuction is typically priced by the number of areas involved:  in this case, it would be four.  You would have to ask the plastic surgeon with whom you consult about his or her prices. There is usually some economy of scale.

Hello and thank you for your question!
In my practice arms, and thighs are considerate two different areas, but you should discuss this with your PS, to see what is best for you.
Good luck!