Add in the cost of buying a mill such as a woodmizer, or renting one. A good friend of mine had a similar idea when building his new house (5000 plus square feet). He bought a new portable mill, had lots of timber from clearing 5 acres, but in the end I don't believe he actually used much of his own lumber. I think the majority of what he cut he did use for formwork though, figured he saved a bunch there the last we talked about it.
And like woodsman said, if it isn't cured properly, it's all going to warp/crack etc and you will be cursing all your time wasted.
Wood-mizer makes some fine equipment. I worked at a small site once when on "vacation" from the M&B sawmill I worked at (tailsawyer on a 8' Letson & Burpee rig).