When bugs cost users' money (airbnb's in this case)

What is your responsibility when a bug affects a user? Does that responsibility change when it costs your users money? The regrettable inevitability of bugs in software has been documented by greater than I and to begrudge their existence would be as pointless as someone with 1 karma posting on HN (oh, wait). More interesting is the responsibility a developer feels (be that an individual or an organisation) when a bug affects their users and how the user's loss affects their reaction. I've worked on various consumer and business facing products and have always taken bugs personally, endeavouring to redress the deficit caused by my, or my colleagues', negligence (all be it, inevitable). Mercifully I've never actually caused a user to lose money but I was recently a victim and thought I'd share: I travel to Paris most weeks for work and use http://airbnb.com quite often to stay a couple of nights in apartments around the city. Today I'll be moving into a place that I booked around a week ago and, just yesterday, the owner and I realised that I was charged only a half of what they was expecting. It turns out that airbnb were afflicted by some bug at the time of my booking that meant I saw and booked the apartment for half the cost (this was confirmed in an email to the host that I haven't seen yet, but will later). So that I have somewhere to stay tonight, we've compromised by meeting half way so that we're equally out of pocket (and I'm going to look after their cats, which is actually a bonus). Clearly airbnb aren't going to cover the cost of their mistake as this would expose them to much greater liabilities, but what should their responsibility be in this case? I know that if it had been my fault then I would feel pretty bad about the situation and grovel like the pathetic wretch I am, but would I feel compelled to compensate? Perhaps personal responsibility has give way to corporate necessity. Still, seems pretty off to me...