Final answer:
In the sentence provided, the subject is 'Blonde dogs', which is the main focus of the discussion.
Step-by-step explanation:
The subject is the nucleus of a sentence, around which the other parts of the sentence are organized. In the sentence "Blonde dogs are easier to sell than black ones", the subject is 'Blonde dogs'. This is the main focus of the sentence, indicating that the topic under discussion is the ease of selling blonde dogs in comparison to black dogs.