Enterprising or greedy?

Recently, I was talking to someone about the Bücherschränke - public bookcases. She mentioned that dealers now go to these glass cabinets dotted around the town to take the books and sell them. I thought, at the time, that this was enterprising.

However, yesterday, on the way to the gym, I saw a man holding his smartphone up to the book covers and I realised that he wasn't a dealer with a knowledge of books, he was just an ordinary man who had an app like Momox on his phone, who could hold the book under his phone and use the camera function to assess how much Momox would pay for the book.

I sold a few of my old books this way two summers ago. On my computer, I typed in the ISBN number and could then see how much  - if anything - Momox was willing to pay for each book. Once I had over ten euros worth of books, I could then send it to the company free of charge.

However, I somehow felt it was 'cheating', the way the man was doing it. He was using other people's books to make a 'quick buck' (as the Americans would say) and cheating poorer members of the general public of the chance to read interesting books.