If you go to theopenmat.com and try to sign up for a TOM Prime membership, you get to a page that says you can have a 3-year membership for $69.99. If you click on the Join box, it tries to take you to a page called tom-prime-membership-4-year and tells you the page doesn't exist. If you manually go to a page with the 4 changed to 3, you get a page that says the 3-year membership will cost you $74.99, which works out to the same $2.08/month as a 2-year membership.
I don't know who's in charge of this page, but I think it needs some work.