Hello! I'm someone who plays Howrse very casually.
Feel free to check my horses for sale tab and make an offer, I usually put my sale horses in direct sales at 7 years old, but I will sell before that if requested. I mostly specialize in Arabians and Argentinian Criollos. I occasionally will have a unicorn for sale.
Foals are sold for 1000-1,500
Adult horses are sold between 4000-7000
Unicorn foals are 10,000-15,000
Unicorn adults are 20,000-50,000
Prices depend on skills, gender, and coat of the horse in question.