I am on "gathering parts" mode right now so I can offer my thoughts.
Pogden (link above) built a terrific setup and I almost went that route. However, I like the idea of setting the controller to some mash temp, walk away and come back later knowing the water is ready, so I went the PID route. Here's my breakdown so far:
Element Package from eBrewSupply - $95
PID/SSR/RTD Sensor/Heat Sink from Auber - $133
Contactor/10ft 4wire dryer cord/L630R outlet/PVC Box - $55
Right now, I am under $300 for a simple/safe PID controlled panel and electrifying the kettle. It's very similar to Pogden's build except I went the PID route instead of SSVR. It's the miscellaneous stuff that runs the tab:
30A GFCI breaker and outlet in my garage - $100 (I did it myself)
Misc (JB Weld/Food Grade Silicone/Multimeter/odds & ends) ~ $50
And finally, I am still debating but I may go for the Greenlee 1-1/4 round punch to make the holes on the kettle and element kit. That's an expensive tool but if I end up buying it, I may list it on eBay once I am done with it. I only need to cut 2 holes. I could use a step bit but it's a big hole to cut and to minimize the chances of a leak, I would like a very precise cut.
I have a pump but I already built a control for it and it's connected to a GFCI outlet in my garage so I don't plan to add that capability to the control panel.
Hope that helps.