I agree that some things are just priceless.
I thought the $5000 was a typo, in fact I had read the figure as $500 until someone pointed it out yesterday.
So off to Uncle Google I went and found:
Instructions on how to build your own pizza oven - $23 - but further down the add the seller mentioned that he spent thousands of dollars in materials to build his.
Another place is selling a pizza oven for several hundred dollars. It comes in pieces that you put together yourself. It's just the top bit, no base.
I've already got a pile of second hand bricks here that I have been intending to use for the purpose. After five years I had better get cracking! Too many Thursday nights recently watching the food shows on SBS has me hankering for a pizza oven. The new stainless steel BBQ we bought last year, even with pizza stones, just doesn't cut it.