Shutterfly.com charges 15.99 for a single custom calendar, and will send a quote for orders 50 or over.
I’ve seen calendars from them and they are very nice. Obviously, it all depends on the resolution of the image so we should be sure that images we choose are high res. The Gallery sizes pics down to 800 pixels wide, but if you click on the pic again it will load it in its native size. Perhaps we can contact the providers of the pics to acquire the highest res image possible.