I did some more investigating and that link above actually talks about
inductive balancing. The parts for the power section look pretty cheap ($2.50/cell?) but driving those "floating" mosfets could get interesting. But you could use a 328 for starters (also floating?) with 6 cells per cpu, plus i2c communication between 328s or something. I don't really know what I'm doing
just trying to figure it out. They discuss the losses in capacitive balancing in that page somewhere. You can see from the schematic below that one can "chain" power sections for any sized pack in an inductive setup too.
schematic from:
http://www.ti.com/lit/ds/symlink/bq78pl114.pdf (discontinued).
power section (8 amps?):
2x 3300pf $0.60
2x 22uf $0.10
2x 20k $0.10
1x 2k $0.10
1x FDC6327C $0.33
2x MA21D3800L $0.17
1x 4.7uh $0.23
Total ~$2.53 per cell for the balance power section.