Do I trust them to undercut the price I think is reasonable? Do I trust them to tell me what the software is really worth to them? Do I trust that they will value my time appropriately?

That's why I have a problem with the word "trust" in this context.

Trust does not mean they won't negotiate hard to get the best deal they can. Trust does not mean they are obliged to show you their cards. Trust does not mean they value your time as you would.

I suspect you'll be very disappointed if you consider the latter to be trust issues.

Instead, trust is a highly multi-dimensional, culturally context-dependent concept. As such, I get little guidance from the phrase "trusting customers works", when I know that each aspect of trust has its own set of parameters, including some where I have no experience to guide me.