General Horse Value help

So, since I'm still pretty new here and am considering selling a few of the horses I have, I'm wondering how much they should be worth. I'm not sure how the pricing goes on here, but I know that I've seen quite a few horses priced in the 20k+ area. So what factors play into value when pricing horses? It's all so confusing and I'm completely clueless on the values of my horses. If anyone could help me, that would be absolutely wonderful! Thanks in advance to all who answer!

In the Guide here titled Hassle Free Buying and Selling is a section called Pricing Factors that give you some idea of what different things matter to buyers and sellers. However pricing horses is really a subjective game and you have to price for your audience as well, i.e. if you're selling starter stock to newbies you want it to be cheaper so that they can afford it. The old rule of Thumb was 10k per 100 stats, but as stats have gotten easier to obtain and other factors like color and conformation has been added that standard is outdated not not as widely used. 

Thank you so much Sabriel! I will definitely take a look and see what I can find. I got a few from the Equine center, got a few from the rescue center, and bought a few from the previous owners.