How to hire a software development company?

I've got an idea for an app that I would like to develop for the web and iPad, and I'm having trouble deciding who to work with to develop it.

I've posted on r/forhire and Upwork and have received countless applications and had about 15 zoom meetings going over the software.

The range of quotes I've received is astonishing, from $5k to $80k.

I'm doing research and looking at the portfolios of all of them and have asked about tech stacks and hours.

Any tips on weeding through the applications and hiring the right team?