Aren't sales people "cheap" as their salary is negligible compared to sales bonuses if and only if they exceed their sales quota?

Not usually. Oftentimes sales people have pretty high base pay. Last time I worked somewhere with a sales force, their base was the same as the engineers with the same level of experience, and then they got commission on top of that.

I don't know. My bosses claim good engineers are a nightmare to find. Cash is surely not the bottleneck.