Using an ATiny for the controller. This is a pretty simple…well for a electric inclined person…build. I think its under $50 in materials…hard to tell since most of the sthttp://www.hackerscapes.com/2014/11/anemometer/uff has no prices with it.
http://www.instructables.com/id/Real-Time-Wind-Direction-and-Speed/
Oh if you end up buying Adafruits’s anemometer instead, good forum note here on how to hitch up to it.