I don't remember the exact amount but IIRC it would have been around $80. $50 for the fountain pump, $15 for carboy holder, plus bucket and pvc fittings. You can obviously do it cheaper if you have any of the parts already, but I didn't and I have other projects I would rather spend my time on.
My basic cleaning process is to do a brief rinse with hose/sink to get out majority of trub/hops. I fill the Mark II basin up with ~1-1.5 gallons of hot water and add PBW/oxyclean, place the keg/carboy on top and make sure it's centered, then plug the pump in and let it run for a while. I usually swap out the hot water and PBW solution at least once when it gets cloudy, then rinse everything and do a final cycle with hot water only. The basic process is the same if you make your own. I wouldn't use starsan because I would imagine the foam would get out of control, plus there isn't really any benefit to circulating the starsan.
For sanke kegs, all of the liquid is coming out of the hole which is only ~2" wide so there is little if any spillage. Corny kegs splash some because of the wider opening, although I've found keeping the water level higher helps this. When I clean kegs inside I usually put a towel under the washer to catch any spray.
If you haven't done so already, search youtube for "keg washer" and you'll find videos of both the Mark II and diy versions in action.