C Craft, I purchased the aluminum from Midwest Steel & Aluminum. It cost $215 for the aluminum (plus shipping). Aluminum cuts easily on a table saw, so I combined pieces of the same thicknesses to cut cost as much as possible.
I always love a grinder built! Post it up! I totaled the build cost for a kmg clone and it came out to about $100 in steel. I already got pretty much everything else.
$100 is about the same price for a grinder build using all aluminum, and I think that would include a 1-1/2" tool arm..... I think anyway. For sure the total frame, tracking/tension arm, and mounting plate.