i think sometimes it can be helpful to work through other possibilities. i think deep down we all have our 'thing' that to an outsider looks frivolous, but to us, is important for whatever reason. maybe he has a long commute. a nice car on a long commute can make a huge difference. maybe he likes to go driving on the weekends to relax. maybe he and his SO enjoy getting away. my H and i have talked about buying a fancy sports car when we're older and retired (many, many, many years into the future) and enjoying long road trips - just the two of us - in our sixties.
or maybe it's just a frivolous purchase that was fun and maybe by other standards, shallow