If a company ask me for similar paperwork (which they have) I have the paperwork in order and ready, they sign a NDA and I am sending them. It's just a step in the sales process imho
A company that never did a pen test or security audit or doesn't want to share them doesn't give me much trust to use them as a partner.
In this case it's not so much about a $100 spend, it's about them potentially leaving a lot of money on the table if they are incapable of delivering the reports in question.
Based on what I have experienced, those that have real decision making power in companies that will make a high six to seven figure purchases simply do not have time to vet their home projects where they are going to spending $100/year. The grandstanding arguments about importance of their projects come from people who probably won't even spend $100/year
You make it sounds this is ridiculous to do a security assessment or to ask for such paperwork. I can tell you that my company insurance even demands it. At the moment I prefer to pay 3x more and store things at a cloud provider which shares these kind of documentation.