Conversations like this a meaningless without first determining what kind of software are we talking about. If it's a first version made quickly to test an idea

Conversations like this a meaningless without first determining what kind of software are we talking about. If it's a first version made quickly to test an idea, the ideal would be 0%. Rapidly developing product, 40%, mature product, 60%, database (like Postgres or SQLite) - 100%, and any software that deals with money, health and airspace should have each live of code covered at least three times by completely different tests, both unit and integration. There's not one size that fits all in software development. And if you don't specify what software are you talking about, everybody will explicitly talk about their own domain and experience.