I stumbled on these unbranded action figure stands on eBay, and they come directly from China and the Far East. While sold as Doll Stands the clip piece works really well for mid-range action figures around the 6" mark.
Cost wise these come in around 50p per stand, very reasonable. They are sold in packs of 5 or more and the seller I used shipped and delivered in under two weeks. They stands come in three parts - the base, the stand and the clip.
The stand clips into the base and the clip then slides down the stand - adjustable for which ever figure you are going to use.
The plastic on these is not the hard crisp plastic of the Figma or Tamashii stands, but is quite flexible. That has the benefit of being a little bit more robust, but also means these are prone to arriving misshapen - and for 50p a stand its often not worth complaining.
The clip is not adjustable in its width, but being a softer plastic it can be clipped onto most mid-rage figure waists. It has two rounded ends to stop paint damage.
While most will use this as a flight stand of sorts, there would be no reason why you couldn't use this as a standard stand or have the figure stood while performing some action moves or other. If you wanted to hide the spine of the stand it wouldn't take much to trim this down.
I started by putting 6" figures onto this - here you can see our Mk47 Iron-Man (Marvel Legends) and Boba Fett (Star Wars Black Series) giving it a whirl.
General Leia here is showing how it would work as a more general stand.
The stand also works for slightly larger 7" figures like the Diamond Select Iron-Man in the final picture. The only watch out here is that the heavier a figure is the more bend is applied to the upright piece and after about 7-days of testing this on the Diamond Iron-Man he did eventually bend so much he came over on himself - there were no such issues on the lighter 6" figures.
As a cheap and cheerful option I have a few of these dotted around my displays and plan to order more for future figure additions.
If you want to find them on eBay then the search text "5pce plastic doll stand" should find you what you want. There are even coloured versions in pastel pink, green and blue if you want them.