Honestly, value in this game is pretty fluid and subjective because there are so many different ways to play - so horses will have different value to different players. Wilds will usually have a higher base value, and wilds with rare/unique markings will also have higher base value. Some players seek color, some players seek high PS and all green BS. 
I usually start my 4*+ horses at $7,500 and go up depending on training boost and PS since Hanos don't really have any rare colors or markings. If I'm selling one of my home-bred foals with high training boost and high starting PS, I list them for more. I have not had issues selling high PS/TB horses and foals for $12,500+. 

Thank you !! I appreciate it :) 

i have to agree with what reddRookk said certain breeds/colors/stats may sell better and some might not id suggest looking at the market first to see what other are selling and go from there. but you can also always ask in the price check channel in discord lots of friendly and nice people there:)