What is the strongest signal of wealth in your opinion

Getting an IVY league or better college education post 40, especially if it is a full time course. Bonus points, if it is an obscure yet developing/cutting edge research STEM/Governance degree.

When you start valuing your time (and where that is spent) over money.

Don't do expenses for show-off at the same time don't hesitate to spend on things which make you or your loved ones happy.