Looked at the cob oven site and it looks very interesting, somewhat similar in ways to mine. You don't juct cook pizza in them, they can be used for ANYTHING and EVERYTHING.
Quality Firebricks and insulation is the key. Admitedly, it does take some 3hrs to crank up to the right temp (750 degrees F) and only 2 minutes to cook a pizza. For all that effort, you then need to bake the bread afterwards to make it worthwhile. When I am finished, I close it up with a solid lid and it is still over 150 degrees F the next day, Then it takes no effort to get it back up to cooking temperature.
I engraved 2010 (build year) on the front of the brickwork and I tell anyone who cares that this is how much it cost me to construct, keeping my costs down by sourcing recycled bricks etc. I just brought new firebricks, heat resistant mortar for the internal firebricks and vermiculite insulation for under the ceiling. All the bricks and roof tiles were sourced for free. I did not include the fuel cost in traveling all over Sydney, Australia to source the secondhand bricks.
Once you have such a great oven, you have it for life, or until you move. A very good investment and I say "go for it"