For what i saw till now,horse archery was really nerfed with all the new changes,specially the lvl 31 , or 32 hard cap. They do little damage now,too little,i dont know about the accuracy but seem that with the new low wpf its been nerfed a lot also.
But.... i dont see 510 for upkeep of a palfrey horse is high...(not saying its low anyway). I have to pay for the German sword more than 500 gold everytime it breaks and its not a horse,its just a sword.