The price depends on how many mutations it has and the species. Pets will be released in around a week of being moved to the stables if they are not bought or breeding. They are in the stables and hatchery.

0-1 mutations = 800 gold sale, 100-150 for breeding

2 mutations = 1,000 gold sale, 200 breeding

3 mutations = 1,500 gold sale, 250 breeding

4 mutations = 2,000 gold sale, 300 breeding

5 mutations = 3,000 gold sale, 350 breeding

6 mutations = 3,500 gold sale, 400 breeding