"What did she buy the photographs of Moscow for?"
Translation:Зачем она купила фотографии Москвы?
I agree. Question 'why': "Why did she buy so and so?" ("Почему она купила ...?"). Answer 'why': "Because she had been told that it was a good idea to send it to...". Question 'what for': "What did she buy this for" ("зачем она купила ...?"). Answer 'what for': "To send it to..."
One of the reasons I like Russian language so much is shown here... not that I know so much Russian, far from that, but in my eyes (Netherlands) Russians can say a lot in a few words... kind of a secret layer, double meanings of words and both are intended to be communicated at the same time... maybe that's why Russia has many poets. :-)