I always use the ACS when pricing my pets. That, or for some, I use general judgment and price them. Blacks sometimes go for 5k, which is way too cheap, in my opinion, and I can easily sell them at 50k if the name is decent. That's much more than what I would have gotten if I followed the ACS.
I find the ACS is better for pets with higher rarities or values, such as species and color.
And you need to narrow your search.
For the price box to the left, put 1, then put 'search by price'.
That will only show you priced pets and leave out the ones not for sale. Also make sure, if you intend to look up sales, you search through rancher shops and not any.
I hope that made sense.