Not sure about new Vitas, but for used Vitas it was fairly easy when I was buying one last year to find a loads on really low FW. Was defo a buyers market.
The problem is when it comes to the Switch most ordinary people will have updated to at least 3.0.1 for Mario and whatever other games are coming soon that need a higher firmware. The only people that keep their Switches on a low firmware and are looking to sell are generally people who want a profit.