As was stated in this thread at the FCP forum, if you're going to use iPhoto to do the "contact sheet" layouts, also use iPhoto's editing capability to desaturate the pictures to B&W before printing. Or,
Way #2- In a simple going-over of the basic "Print" dialog box, you will see three pulldown menus.
Top one allows you to select which printer you're going to print to.
Second one allows you to choose between different printing presets you may set up, like "Standard," a draft mode, oddball paper size, Black and White, etc. without having to go through many items each time in the third pulldown menu...
Third pulldown presents ten or more aspects of the print job that can be changed from the defaults. The one of interest to you is "ColorSync." Select it, the ColorSync selections appear. Use the second pulldown menu "Quartz Filter" to select "Black and White." Hop up to the Presets pulldown and select 'Save As..." Then you'll have a B&W preset at easy reach for next time.
Not really sure that there's much savings to be had. Many inkjets now use the color inks along with the black to create a greyscale image even in B&W mode.
The best and cheapest way in the long run to print B&W, especially in large volume, is to get a laser printer. Always prints B&W, toner cartridges are really cheap when cost is spread over the number of printed pages they yield, especially compared to the ripoff prices for inkjet cartridges, and recycled, refilled cartridges are even cheaper. Some "personal" laser printers can be had in the hundred-dollar range, but typically $200-300 depending on make and features. Just seems like a no-brainer if the cost of printing ink is an issue, and it immediately solves the color/BW print issue too.