1) Klei Kodesh are those with actual specific community responsibilities, with teaching Torah being the most typical. They dress out of respect for those responsibilities, not to advertise personal piety. Even the best boys just past Bar Mitzvah are not Klei Kodesh. edited
2) If one dresses in same colors on Shabbos as during the week, unless you see them both during the week and on Shabbos, there is no way to tell whether they are dresses LeKavod Shabbos or just because they have a large clothing budget.
3) Black Tie events are not that common even for the wealthy. Formal dress is generally worn in honor of the Bride & Groom.