Not sure what you mean. Prices would be set in order for supply and demand to even out. The startup is unlikely to use undocumented supply because of risk.

Don't understand the second point either. 20% margins is plenty. See: http://abovethecrowd.com/2013/04/18/a-rake-too-far-optimal-p...

And tech-driven businesses have lower marginal costs thus can succeed with lower gross margins.