jpe I understand your concerns very much. And certainly by all objective measure, a one-time payment of 3$ is far more affordable than a monthly 4$.
At the same time, the reality is that this was an unsustainable model. As a professional mobile and security engineer, Master Password's model only affords me about 1 hour / month of development time. This app and the novel solution it offers its community deserves more than that. Building out an independent identity platform requires more than that.
Scaling up the one-time payment model to what would be required for this was unrealistic and could do little to reduce the financial risk associated to it. I think we all want to feel confident that Spectre isn't going to go away.
Although it is difficult to communicate the value of attention to code quality, security research & maintenance and technology upkeep to the average user, if you're looking for where the value of a 4$ monthly is, it's in the answer to the question, "am I willing to pay 4$ to support this one engineer's full-time occupation of bringing this solution to the market and to my devices?"
Thankfully, the answer to that question doesn't need to be Yes, and everyone's capacity for contributing is different. This is why it's always been crucially important to me that Spectre is both Free Software as well as available to everyone at no cost.
Please don't hesitate to make your ongoing concerns heard.