There are some studies which reveal possible connections between wealth, compassion and how generous people are. [1] and [2] for articles about studies like [3]. I see some shortcomings in some of the studies (looking at drivers of luxury cars is not informative about all types of wealthy people, just the ones who care about spending it this way which self-selects a certain kind of person), but I think that the general direction could be informative for more research. There are also studies about cognitive costs of empathy [4] which may relate to this.