I was amazed that how I'm getting these users.
Now after 8 months I'm thinking about to make some money or to try to get some more users, I ran a survey people said would love to pay 5$ a month but no one converted when I added premium modal. So, I moved back to free and started thinking about adding ads, but ads were making user experience so bad.
I removed them as well. I need some idea if I can make something out of it. Or I should just leave it as it is.
"Hey mom, what do you think of my app?" "That's a lovely app dear. I'd definitely pay $5 for it"
You have learnt a valuable lesson. People will say one thing and do something else. Users actually paying you money is great, not only because you get money but because you get strong information that what you have made is valuable to them. (The above example is drawing on the book The Mom Test. I definitely recommend you read it)
Most engineers build software backwards. They start with a solution and go looking for a problem. They make the fastest, shiniest, neatest solution to a problem no one actually has. (How do I know? It's exactly what I did with my first startup!)
Imagine a dating app. It takes 30 seconds to open. The pictures only show up in black and white. The app crashes half the time you try to send a message. But it always gets you a date on a Friday night. It would be the most popular dating app in the world.
Try to find a problem that is so important and valuable to people that they will pay for your app even if it is slow, buggy, ugly and broken.
As it is you have happy customers paying nothing. You don't say if 280 is sign ups or active users (you do need to measure that). You might expect to convert a small percentage, maybe in single figures, but only with something they need (see 1st paragraph).
But you're learning that when you give people something for free, they're happy to use it for free. And for something as simple as "tracking expenses", it's really hard to add enough value to get people to pay. I mean, I can do it in notepad, or with a pencil and paper...