So how many B&W prints could you get out of an Epson 2400 inkset?

I'm contemplating an Epson 2400 or the new 2880, but the ink expense gives me pause. I would get a 3800 but I need something more portable.
I'll be printing mostly 11x14s.

If you want to do B/W right you would better off purchasing a Nyson bulk ink kit for Septone or Cone inks. This produces a superior B/W image because color is not used to make gray. If portability is an issue you can use prefilled Epson ink carts with these inks.

I use a Canon ipf5100 and get excellent results printing B/W with all kinds of toning possibiities. I also have a pair of 2200's one outfitted with the Nyson ink system and Septone (cold/warm tone set). The 2200's never get used and I am looking to sell them.

I use an R2400 with the Fotospeed CIS, it gives excellent results, only using the minimum of the lighter colours to tint if desired. Otherwise, the grays given by the three black inks are beautifully neutral and smooth.