I don't know about deals on replacement cartridges but I haven't bought any for my lexmark Z11 for at least 2 yrs - the cartridges are easy to refill & refill kits are cheap & easy to find. I guess the print heads on the cartridges will eventually wear out. By that time I think I will just replace the printer.
Check out these sites for ink:
http://www.inksell.com/goinksell/inklexmark.html
http://bizrate.com/buy/products__cat_id--49,keyword--Lexmark%20Inkjet%20Refill%20Kit.html