It's something that I ever asked myself and recently I have somebody asked it to me again: what free (as in free beer or as in free speech) video editors are there?
A video editor is a very complex piece of software to develop, so there are not many free solutions, the few ones that we can find are not very good and the ones you have to pay for are quite expensive.
There are other types of complex software developments like web browsers and office suites, but a video editor can be even more complex and in addtion it has very specific and small user group, so they will have less ability to attract volunteer developers. Everyone use a web browser, but too few people use a video editor. It is difficult to entice a developer to devote their free time to a project so complex and with so little reception as a video editor and those who do it, won't expend the same effort. A web browser and an office suite have a much larger user base and therefore may attract a larger number of volunteer programmers willing to develop a free version. So there are very good browsers (Firefox, Chromium) and office suites (LibreOffice) and sometimes the free version may even exceed commercial version and although part of their development is done by volunteers as a hobby it also gets support and funding from major corporations and foundations such as Google, Mozilla, Oracle, Apple and Apache. Actually, none of the success stories mentioned departed from scratch but it originated in a commercial project freeing its source: Firefox comes from Netscape, LibreOffice from StarOffice and Chromium ... well, Chromium story is a little different as it has always been free software (KHTML), although it would have been impossible to exists without the contributions of Apple and Google to its WebKit engine through its commercial projects Safari and Chrome, respectively. So to have a free video editor that can compete with commercial versions, we will have to wait for Apple releasing Final Cut source code as free (don't expect for that right now).
In addition , those who have already worked with video editing have proven that it is a resource-intensive task (processor, memory and hard drive), so a video editor has to be efficient and well planned, adding more complexity to the project.
For all this, the few free solutions that are can't compete with commercial software: cut video pieces and put them somewhere else, add some simple effects and little else. As my video editing needs are very basic, with LiVES I have more than enough. Another solution is VLMC from VideoLan people who often do things pretty well (VLC Media Player), but the last time I tried VLMC was still in a very early stage of development and very limited, it was little more than a sketch. I don't know how VLMC have evolved since then, but I would not have much hope now.
An often recommended option in forums is Cinelerra, but my experience with it was disastrous because its instability made it unusable: every time I tried to do something it either hanged or closed, it was impossible to do anything.
But overall, my experience with video editing free software goes back some years, so it may have changed, hopefully well.
As for affordable commercial software, the thing is again complicated: complex software intended for a small group of users makes it a big effort to pay by a few, which makes it not very cheap. Moreover, these two reasons also cause few options reducing competition basically to Adobe Premiere, Final Cut and little else, so competition to offer good products at a good price is not highly favored.
Anyway, my experience with video editing is poor and old, so I encourage anyone wanting to do it to try for yourself the programs available and if you like then you can correct any inaccuracies I may have said in this post.
In Wikipedia you can find a list classified by free and paid, and a comparison table of the features supported by each.