One of the most common misconceptions about PWAs that I encounter these days is the notion that you have to build an "app".
If you have a good responsive website and supercharge it with PWA capabilities, THAT IS A PWA!
And this is important to realize when we talk about budget. This is why the path to a PWA might be less expensive than to a native app. You don't need to build a website + PWA, the website can be your (should be?) your PWA.
If you know you will build a website/webapp for your project, the cost of a PWA drops significantly compared to website + native.
Sure, a PWA will not always be the best choice. That really depends on what you are going to build. But somehow, a lot of folks seem to be under the impression that a PWA has to be "an app".