At this point, Prime doesn’t make sense if you want to save on shipping. It made sense because it included a lot of good stuff (video before ads, some music, shipping, games) but just for shipping, there were better options.
I basically overpaid but didn’t care out of convenience - partner sometimes watched prime, I ordered occasionally, played some included games. But the changes to video were so shady that I cancelled it.
I have full IPv6, none of my ports that I haven’t explicitly whitelisted in the firewall can be accessed from the Internet. I can open a host completely, but it’s not default. This is on the most common brand of consumer routers here.
Just because it’s not NATted doesn’t mean there’s no firewall in place.