I completely agree with @Mr_FI_Fox with this one. Not everyone can afford it, and pricing people out is a terrible idea. Some people may find transitioning to password managers inconvenient and have no motivation to do so. Making a premium plan a premium price would be even more of a reason to push them away.
Lets also not forget that they make their money from paid accounts. Free accounts take up space and compute power. They want people to want to upgrade for a reasonable price so those costs are covered.
The big income source would be from their business/enterprise side of things. This pricing is tiered based on the number of users, which makes sense. If anything, this could be slightly increased, but I would like to suggest a separate option for non-profits and this option. Whether it’s half priced, x number of users for free, etc. They could partner with TechSoup and get validation through them.
They could also add a donation button, or perhaps a pay-to-vote for feature requests. Say $1 a vote that you can add to it. So if you really want a feature added, you could donate $100 to add 100 votes to it and spike its awareness. Sure, they won’t all be accepted, but it could potentially be a good, fair way to do this. This wouldn’t replace the current system, but be added to it. We should still have our free votes. This is more for businesses that may really want a feature, so they can pay to have it added (well, to increase the chance it’s added).