In general it's a fine balance of what makes a v1. It's a huge challenge to identify those features that are must have vs those that are good to have. A poor v1 experience will chase your early adopters away and I doubt many people give a second try at all. But a delayed product and late or no feedback from users would result in building a product that is tangential to what the user actually wants. No amount of user studies would fill in that gap. In this particular case, however, if I'm listing down all my expenses, I definitely would also want to sum it up and expect that sum to automatically update too. If I and those who think so are in the minority, well and good. For an app so elegant, no one would want or hope it to fail. But if you are releasing the app and not expecting or ready for honest feedback, I can't see a point in releasing it in the first place.