Another source of profit "to the blockchain" or Hive ecosystem (but not directly to DHF) is the 5% fees on conversions from HIVE to HBD. That's not necessarily attributable to the stabilizer even if the stabilizer is the one doing the conversions, because others might do them anyway, but it is a part of how fluctuations in the HBD peg pull value back to Hive over and above the utility of HBD to the platform.