The top 1% by household income in the US is about $500k a year. There are more than 100 million households in the US, so that's conservatively at least 1 million families who could afford to support a 5 figure microtransaction whale. That's a lot of money!
Lot of kids/young adults with old money is my guess. These people will never have a reason to work so will pad out their days with things like this.
If you're on a million a year, 30k is about 11 days' income.
Why are they throwaway?
Some of the people who can buy 30k watches have so much money that it can become just another throwaway item.