I have a 3/8 50' copper chiller I made in my workshop, I also stir the wort with the chiller and the water coming out of the discharge hose is piping hot, when it cools down a little I stir some more.
I've never kept track but I'm fairly certain it's around 8 minutes or so to cool 5 gallons of boiling wort to 75-80 degrees. This is ofc using water from our hose bib in winter... that might play a factor but stirring is the obvious accelerator.
Ohh, and the 50' of copper cost me around $45, the fitting I used for the hose bib (well, 2 fittings to compensate for the size) cost around $8. All in the project cost around $50-$55, not too bad