He must be doing something to save time relative to, say, a cuemaker who makes only 200 cues a year (whatever that is, it seems like it has to be more than just CNC). But that seems to be offset by his low prices -- in part becuase of whatever makes his costs low, and in part because of the large supply he puts on the market.
Overall, while it's not really something I would buy, it still seems like a reasonably good deal: $300-$500 gets you a lot of inlay work, cues that I've never heard anyone say warp or have points lift, 2 shafts, and a design that no one else will have. I've hit with a friend's, and it seemed fine.
As far as his selling on Ebay, why not? He can sell through distributors and they'll want to make 20% or more on each cue. Or he can pay 2-2.5% via Ebay and split the 18% savings between himself and his customer.
Cory