TIME. Time is the MOST precious commodity. Help users SAVE TIME. Save time finding something of value to the USER. You can't "presume" how much to charge. You have to "TEST" pricing then keep jacking it up until your customers don't pay. How can you pay for something what does not offer value. Stay small. Stay NICHE. Grab a slice from a BIG market. Forget millions. slap-yo-self with fury with delusions of becoming a millionaire, and make a goal of making enough to avoid being trapped in a 9-5 lifer situation. It take a LOT of luck + skill + market segment expertise. Like you have to KNOW the market you are going to be competing in. Assisted living , senior care , retirement calculator is VERY hot now. You'll be at it after your day gig 6pm-2am testing / building / iterating. Good LUCKY. launch a free beta version learn what customers value and how much they will pay ( ask them) THEN when you have enough people crack addict addicted to your service / app start charging. Be merciless. But offer excellent customer service. Always be honest.