Hey,

Thank you for asking. The confusion regarding where to start and how to proceed is very common. Even I had a similar issue.
The cost aspect always depends on how unique and challenging your idea would be. As you can see, many will offer a free quote or free consultation for your query. But they will not talk about the hidden part.
It is always advisable to request help with a blueprint in mind. If you start a conversation without any clear idea about what you want, some may misguide you, and you will end up with over-budget or not the product you wanted. If you are in the market to find the best development partner, I would suggest you look at the testimonials. Customers will not lie!
To get a clear idea of what the company is all about, start reading the customer success stories. How big the customer was and what they needed will tell you all about the development capabilities of the partnering firm.

GOOD LUCK!

To add further-
In order to shortlist the best mobile app development services options in the market, you may take the help of third-party review sites. There are some prominent sites like Clutch, Best Mobile App Developers, IT Firms etc, that offers honest listings and reviews. I was able to find valid partners through them. Hope this might help you.