@Maria11831 It's not Airbnb, it's the guest who got a 30% discount. The guests who receive discounts almost always mark the stars down. I asked a psychologist I know who is also an Airbnb host about this and here's what he said:
"Many of the most entrenched complainers are entitled people who, among other things, believe they are entitled to discounts and to paying less. They are over-valuing their own needs and under-valuing the needs of the host. It’s a kind of selfishness, or it could issue out of the profound self-centeredness that is related to Narcissistic Personality Disorder, or it could just correlate to the narcissism of a person with inadequate feeling development or ability to put themselves in anyone else’s shoes.
"If people are wiling to pay full price or a higher than average price to stay at an Airbnb, this in itself indicates that they understand they are willing to pay to get good value. It shows that they have an understanding of the host’s need to be compensated for all the things they are providing. The worst complainers are likely to be people who don't think they should have to pay to get value — so they will be seeking discounts and less expensive stays."
So it's neither illogical nor a conspiracy, in my opinion.