The Nashman likes buying his produce from sellers who actually know what they are selling. You can't get that from SM or Rustan's. Overpriced na nga benta nila, of dubious provenance pa at sobrang kikintab ng mga prutas kahit out of season. In the city market you can haggle and practice your drama skills. You can make pakipot, the seller can make lambing, and you can engage in banter. Try doing that at SM or Rustan's.