Why exactly would you have to be sneaky? THEY marked the price, its not like someone went around the store taking price tags and switched the products.
As a consumer, we see a product we want, and they price they are asking and determine if we would like to purchase said product for that said price. Now its the consumers job to make sure these companies are getting the most bang for their buck? Sorry, life doesnt work that way. As a consumer its OUR JOB to find products we want for the best possible price.
Not to mention, perhaps petco shouldnt be in the pet biz if they dont even know how to correctly price their animals. This is America last time I checked.