Making a good user interface is definitely not easy. Yet it's orders of magnitude easier than writing ffmpeg.
That said, there is nothing wrong with a paid wrapper around a large and complex open source library. Distributing their work more widely is not a disservice.
> Yet it's orders of magnitude easier than writing ffmpeg.
If there's one thing that I've learned, is that "It Depends™" is my mantra.
ffmpeg is the sharp end of years of work by a whole lot of folks. It isn't just a single developer's "pet project" (although its originator[0] deserves enormous heaps of credit). It has been maintained by a whole community of really good (and dedicated) developers (and people with all kinds of other skills)[1].
It's not just a library. It's a platform. People have made entire (lucrative) careers, from just "tuning" ffmpeg.
Because of the infrastructure provided by ffmpeg, people can build some really useful implementations, and create focused applications.
I have found that making an approachable interface for a complex substrate, can be incredibly valuable, and definitely worth paying for. It can often mean the difference between soaring success, and miserable failure.
"Easier" is in the eye of the beholder. Ever watch a really, really experienced studio musician at work? They sit down, and in five minutes, your scratches on a piece of paper, take on a magical aspect. They make it look absurdly easy, but that comes from intense practice. There was a documentary (don't remember the name), about a bunch of major musicians, that came out of the California scene, in the late 1960s/early 1970s. In it, there was a discussion about someone (I think it may have been one of the Grateful Dead, or Eagles), that lived above Jackson Browne, who is a very successful singer and songwriter (BTW: The "songwriter" part is the bit that makes the money). They talk about hearing him practice, as he was developing songs. He'd play just a few bars, over, and over, and over again, until he got it right.
Songwriters and studio musicians may not be able to command roaring crowds at Glastonbury, but they can give you the album that you'll need, to get that crowd to show up, in the first place. So success requires contributions from many different places, and each has its own measure.
That said, there is nothing wrong with a paid wrapper around a large and complex open source library. Distributing their work more widely is not a disservice.