I'm in medical school and wore a hand-me-down suit from my dad to all my interviews. I did have it tailored beforehand. Nobody once asked me about my suit or my shoes. If they would have, there's a good chance I wouldn't have been choosing that school. Half the interviewees at some of the schools were foreign students that dressed in obvious DI blazers (blue) with old black slacks that didn't fit and a brown woven belt. Looked terrible, but I wouldn't ever judge their ability to be a doctor off that.
I don't know anything about the finance world, but your attitude about his dress just turns me off. Sorry. That's probably why I'm not going into finance.