They have to start somewhere. Unfortunately part of the issue is that most OEMs do not even support their budget models as well as their flagships, so they would fall short of basic reasonable GrapheneOS requirements like 5+ years of timely security updates.
When I was looking, the older models were around $500. Looks like they came down in price. I also looked at used, but my company stipend/discount would only apply to new.
Boo