Bauer's move will sacrifice hundreds of thousands of pounds in cover price revenue, as it looks to showcase the on-going redesign introduced by editor Colin Kennedy.
Bauer claims the cover price drop is a one-off for the November issue, on sale on 24 September.
IPC's rival Loaded, priced at £3.50, said it had no plans to follow suit.
Tactical cover price drops have been used by publishers across other sectors, including men's weekly and real-life titles. But one rival publisher said it was "highly unusual" for a change in the men's monthly sector.
FHM lost its 13-year reign as the biggest selling men's paid-for title to Men's Health, according to the latest ABCs figures, with circulation falling 16.2% year on year, to 235,027 between January and July this year.
The latest National Readership Survey figures, between July 2008 and June 2009, however, show FHM ahead of Men's Health.
FHM is looking to ditch its lager-swelling, lads' tag and introduce more sober content. Its latest redesign has introduced new sections such as health offering, FHM Bionic.