Pets in my 3rd tab of my first stable are for sale along with most pets in my hatchery. Most are under 500G.
Prices go as follows for MOST of those that are for sale:

Each Visible Mutation: 100g
Each Carried Mutation: 50g.

If prices are a bit higher than the following guidelines above, it is more than likely because it has a mutation in each slot- Carried and/or Visible.

All must go or be released Friday the 24.