Incidentally, it's spelled "toupee" (or toupée) for the men's hair piece, which is why it is pronounced "too-pay." If it was spelled "toupe" it would likely be pronounced "toop." This is reflected in other similar words, like brulée (as in crème brulée), and jetée for the ballet move.
Loupe (pronounced loop) is the single magnifying lens thing you look through with just one eye.
Troupe (pronounced troop) describes a group of people doing something, usually like a dance troupe or a musical troupe.
So more generally, words that end in "-oupee" and "oupe" are pronounced with the "-oo-pay" and "-oop" sounds.
