iPhone:

  BoA - 457MB
  AMEX - 130MB
  USAA - 109 MB

I only have BoA because I haven't canceled my CC with them yet (kept because AMEX is not accepted everywhere). It seems I deleted my other bank apps (after I'd closed the accounts, makes sense, right?) but IIRC they were somewhere in the 150MB-200MB range. Some people just really like bloat I guess.