[twic]

They spent 50 million in cash, received 42.5 in tax credits, and made a donation of 75 million. So effectively, they made a 75 million donation for 7.5 million outlay. It's a very efficient way of making donations, but it doesn't make you better off in raw cash terms.

But being rich is not about having cash, it's about using cash to achieve your ends. Giving 75 million is really buying 75 million worth of philanthropy - 75 million worth of social status, or invites to exclusive parties, or favours from patrons, or support for projects valuable to them. And they bought it for only 7.5 million!