Una API's usability is unclear to us. Most people are completely against webview. If there are real requests and money is not a concern, the price will be in the 50k to 100k range. We will either check the available api or do it as a standalone app using our own api.
UNA has a range of changes in the API and the new settings in the API App for that very reason - native apps. You are right - the cost of development for a medium-complexity app with UNA backend would be in 50-100K range. Right now we are building them for 3 clients and will announce a preview soon.