About 18 months ago I teamed up with a partner to create an app which makes meeting people online safer, using various safety features including video verification and in app security. We often use Tinder and Bumble as case studies-- despite the fact our platform can be used for friendship or romance.
We outsourced development and had our fair share of hiccups. All of which we learned from...at a hefty price.
Knowing what I know now, allowing us to avoid the mistakes we did make, I would say development would cost in the $50K range for a fully functional app like Tinder. You would need the swipe feature, social media integration, real time chat, geolocation, in app payment, analytics, and user feedback-- just to name a few.
You also need to think about API's, admin costs, project management costs, your tech stack, user testing, UI/UX, etc. None of these things I would suggest glazing over.
Monetization is the easy part. You can charge subscription fees, premium features, ads, affiliate programs...and the list goes on.
However, the most difficult (and possibly expensive) aspect is the marketing of the app. Many founders are under the impression that if they build something great, users will come...WRONG!
I would start by first validating your market and establishing a database of potential users. Then, have your app developed from there.
Also, remember developers and business-minded founders tend to communicate on different wavelengths. Ensure you clearly and visually communicate your vision -- every detail is important and should be communicated as you should assume nothing is implied.
I'd be happy to have a call to discuss how you should go about this, as I'd be glad to share my process which ensures lean development costs and active users at launch.