"Man" and "men" are different in pronunciation:
man [mæn]
men [men]
As are some other word pairs:
handyman [ˈhændimæn]
handymen [ˈhændimen]
bogeyman [ˈbəʊɡimæn]
bogeymen [ˈbəʊɡimen]
superman [ˈsuːpəmæn]
supermen [ˈsuːpəmen]
a more complete list:
adman, anchorman, apeman, bagman, batman, bogeyman, cameraman, caveman, chessman, conman, everyman, freedman, frontman, gasman, jazzman, handyman, he-man, hitman, iceman, lawman, legman, linkman, mailman, merman, middleman, motorman, newsman, newspaperman, oilman, packman, ragman, repairman, sandman, schoolman, snowman, spaceman, strawman, strongman, stuntman, superman, swagman, taxman, weatherman, wingman, wireman, yardman
But there are also a lot of other word pairs that are not different in pronunciation, for example:
salesman [ˈseɪlzmən]
salesmen [ˈseɪlzmən]
chairman [ˈtʃeəmən]
chairmen [ˈtʃeəmən]
spokesman [ˈspəʊksmən]
spokesmen [ˈspəʊksmən]
Why?
Isn't it convenient to use different pronunciation everywhere?