50+/year? That is a big plus indeed, I also want my family on Protonmail. I donated btc in the beginning and got on board immediately, now that the bridge software is out, regular people can use their MacOS mail and their Thunderbird so the service is really attractive. But... on my own domain with 2 kids and a wife and a father it is 25 euros per month or 240 per year. I email about once every couple of days, as does my wife. Kids do even less... Now I have 3 mail users for 3 euro/month at transip.com. The price difference is pretty big. A family package would be really welcome. Before you ask, be aware that the "Addresses" of the Plus account are not users, they are aliases.

Edit: I still think protonmail is absolutely great, it works well, it looks very nice. I'd love to pay and probably would switch just for me, however, it's pretty hard to route one address of a domain to one server and the other to another.