Par exemple, vous ne devriez pas payer pour les castings ou les séances photo.

Question

I thought payer could take a direct object: why is the "pour" needed here?
It’s a great shame that alternative answers aren’t provided if you get a correct, "matching" answer in the Writing exercises - the list of possible translations is such a useful tool.

Céline Pickard · Accepted Answer

Bonjour Anne,
In French, you can use "pour" after the verb "payer". In fact, in the English and the French sentences in the exercise the direct object (= "money") is implied: 
to pay (money) for castings ... = payer (de l'argent] pour les castings ...
Also, thank you for your comment about the alternative answers not showing when you submitted a correct answer. I will mention it to the rest of the team.
I hope this is helpful.
Bonne journée !