I've double-side printed my own calendars for the past 4 years with no problems. I printed 7 copies of the calendars for family each year and I think I only messed up a few pages each year--mostly due to not changing the ink cartridge soon enough. And I don't know how much Kinko's is charging you to bind the calendars, or what type of binding you are doing, but it was only about $1 or $1.50 per calendar for me to have Office Max bind mine. Or are you not counting the price of the ink into your costs? If not, I can see why the binding would be the most expensive part
Oh, I also like to use double sided photo paper for my calendars, which increases the cost as well.
I think I noticed some people mentioning using Scrapbooks to Share for calendar printing but I've never looked into this so I can't say how they do it or what the cost might be.
You may want to inquire at places like Office Max as to how much it would cost you to have them print and bind though--it will save you time and frustration, which is also worth something to me!!
HTH!!!