This is pure DM. On what basis have you 'no doubt' that he is 'wealthy'? And people on minimum wage are not 'subsidising his lifestyle', they are contributing to the same tax pot as everybody else. So if they are 'subsidising his lifestyle' they are also subsidising the billionaires whose rate of taxation is less than the PAYE rate for their income would be. And there are many, many people who have fully retired with decent pensions who can well afford their own heating, TV license and public transport. Are they leeching off the state too? It's a dumb thing to equate paying tax with subsidising somebody else and it's the politics of envy and division.
He may be an acknowledged expert in his job. His employer may have failed to recruit somebody to take over. Maybe the systems he designs are a bit arcane, but still used? I'm aware that there are ancient mainframe computer systems still in use in this country, whose operation relies on people well beyond retirement age, because nobody younger understands them. Should they be forcibly retired, and the systems summarily shut down (do consider, some of these could be part of important infrastructure)?
He may just be doing a bit here and there to keep his mind sharp, to keep busy, to maintain a sense of self-worth. Do you know for sure? Why make an example of him?