How to build a $20 47A power supply

[mistercrash]

Pardon me if I seem ignorant, but is there any way to use those power supplies to build something as powerful as this.

http://www.rivergatedist.com/bulldog_90.htm

I had a Rivergate PS years ago and I loved it. It was a 30 amp model which was perfect at the time. But although they are really good and powerful from what I remember, they are way too pricey.