A MM3 starts at $189. The hopper is $45. The AAW motor is currently on sale for $300. Then you'll need some lovejoy couplers (about $25?) and some wiring, a base and misc hardware (maybe another $20?). That's $580 plus some time spent assembling.
A fully assembled, all-in-one alternative with a 1 year warranty for ~$200 more seems to be in the ballpark. Particularly with their (yet to be proven) innovations (fluted rollers, differential speed). As with most of SSBT's products, I think it's priced about right. Not cheap, expensive enough for me to second guess it, but when I look closer, probably about right. It could end up being a dud, but it'll take us a couple years to find that out.