Home printer vs print at Walmart
There are a few other factors that you need to add into your equation to compare printing at home vs. bringing them to Walmart (or Costco, or ?).
On the home side you need to add the cost of the ink. You also need to determine the "convenience factor" and subtract that from the equation. This is amount of money you "save" by being able to print whatever you want when you want. If you buy the Canon 9000 II printer the previous posted suggested (it IS an awesome printer), you can print any size up to 13 x 19 so you would not need to buy a second printer for all your other printing needs.
On the other side of the equation (the Walmart side) you need to add in the cost for driving or getting to Walmart. This needs to include gas, oil etc. You also need to add in your time (getting in the car and driving to Walmart) and the inconvenience of having to do this. Also don't forget to subject the "quality factor" from the Walmart side. Side the previous Canon printer is one of the best out there you need to subtract something from the equation if you want a real nice print but only get an "ok" print. Believe me, this factor alone (when trying to make the girlfriend/spouse happy) is worth the price of a brand new printer every time...