Um, hello. My Navi has no real need for our Charge+1 or Rapid+1 at this time. So, I think I'll sell them off in the hopes of building up zenny for upgrades or new BattleChips.
So, from checking around, I suppose a good starting price would be 1,500
z for each. This price is, of course, negotiable if you want to substitute some of the zenny for a chip or even throw in a rarer chip in loo of zenny all together.