Few people start questions with a preposition. There is a preference in "wh"-questions to avoid using a preposition at the beginning of a sentence.
• Whom would you like to speak to? (less formal but pedantic)
• Who do you want to speak to?
• Who is this gift for?
• Where do you come from?
"Them" refere-se aos itens que estão à venda.
How much will she sell the books (= them) for?
É natural terminar a frase com preposição. A regra que governa a gramática baseada em idiomas latinos não se aplica ao inglês.
wh-questions: "When a question word is the object of a preposition, the preposition most often comes at the end..."
• Who is the present for? (natural)
• For whom is the present? (formal)