DH just built a fairly large wooden deck on the back of our house (I think it is somewhere around 1,000 sq. ft). The materials cost us a little under $2,000, including pressure treated lumber, nails, etc. It took him and his dad 5 days to complete it (and they are not super experienced carpenters). We're planning on staining it next weekend, so I don't know how much stain is going to cost us. Dh described the deck to the contractor who built our house and he said that it would have cost around $1,500 if he had hired carpenters to build it.
I would have loved to use Trex or another composite, because maintenance would be so much easier, but it just wasn't in the budget at this point.
The one tip that I would give you, if you are going to diy, is invest in a nail gun! I think dh found his to be a life/arm saver for this project!!