We had booked to stay at Simon's place. Unfortunately, we had to cancel last minute. Simon wrote that he could not rent out the flat with such short notice, and therefore, he could not repay us. We understood this and asked our niece if she wanted to go to Paris.
She was super happy to go, but when we informed Simon that our niece would use the flat instead, he said he had already rented it out (!), and because we had cancelled, he would not reimburse us as, because under the terms and conditions, he doesn't need to.