Their presentation for investors quotes a sale price of $1000, not $300. At that price they might be able to do it. How well they'll do it remains to be seen.
Their presentation is all about their XY positioning mechanism. But that's not the problem. The hard problem is dispensing solder paste reliably and precisely, sticking the component down, and using hot air to solder it into place. As with low-end 3D printers, most of the problems are where the weld/soldering action takes place. They don't say much about how that's done.
The important thing is doing a consistently good soldering job. Nobody needs a machine that produces lots of reject boards.