sadly i am with you for low food yield from this quest. i never got more than one thousand apples (125 apples and 3k coins is the norms for me). once i was stoked to get over a thousand apples, but game reset kicked in and i have collect the quest again , which had only coin return for me (that is for the same quest).
i was using high level magic for the quest before i bred second (or third ) magic dragon. current second magic i keep is only at lv 3, perhpas that affected the yield as well. i sorta stopped sending it to quest last week before i kept getting coins and for the tales.
after reading this thread, sending in high level (lv10) still did not affect much, just collect and got 125 apples.