"A third person is mostly consuming, spending a lot of money on things like a yacht and plane. While it’s true that the wealth of all three people is contributing to inequality, I would argue that the first two are delivering more value to society than the third."
Really? I always considered this kind of spending a good thing for society. Other businesses and people get that money, they create technology, materials and processes that would likely not exist otherwise, there's still tax being paid along the way and we get a bit of cultural heritage as a bonus (castles, boats, planes, cars, the Sistine Chapel, a lot of paintings - all of which exists only because some rich man decided he wanted it).
Taxing luxury is a mistake and a potential slippery slope IMO. IIRC, the US tried it in the past with disappointing results.