Coming from the grades 9-12 sysadmin side, I might be able to provide some perspective. Every school is wildly different, so I would recommend against applying my perspectives too broadly.
1. Cost: Windows licenses for student PCs are just under $20/PC/year (for us). Is your $5 software 25% as useful to students as their operating system is? Even worse, the reality is if I put your software on my 1000 computers I'll be lucky if 300 of them use it. That's something to keep in mind when working with per-device licenses. I agree installed system software bloat is a problem. That results from every department having different needs. We might be a little different in that we don't allow students to install/run foreign software (using AppLocker).
2. I agree different schools are amazingly different. I collaborate with a few other schools around me and whenever we meet I'm pretty floored by how differently each one approaches basic problems. These significant differences really add up and I can understand how supporting schools might be a pain.
3. It seems like every vendor wants access to my SIS. That's a privilege not granted lightly. I'm generally okay with automated CSV dumps of bare minimum data uploaded over a secure channel, but some vendors have the nerve to request direct LDAP or Oracle database access over the public Internet. No way!
4. I'll agree school IT teams are generally terrible. Among my peers and schools I collaborate with, I'm the only one with a degree in IT. Many are older and migrated to the role from something else (former math teachers surprisingly often). Some find themselves shoehorned into the role because they happened to be the most technically-inclined among the staff. These guys are uncomfortable in powershell/cmd and typically use contractors or local PFYs to handle technical details. Schools do not pay enough to attract decent talent. I could work for a local company and make 1.5-2x more doing less than I do here, but for now I like this environment.
5. While video demos can be helpful product overviews. I distrust video demos just as I distrust other marketing wank. I want to test drive the car before I decide to purchase it. That said, I wouldn't expect anyone to let me demo something longer than 60 days. The long time in my case is that exploring new software is usually a backburner project, and I am likely to have other things come up that take priority. I never put production data into trial software however.
6. Yes, purchasing processes are a pain. I 100% agree. I currently have a request for $60 of printer toner that's been sitting in the requisition process for over a week. Trust me, it's just as bad for us on the inside.