It would depend on what type of bondage items.
If they are traditional fetish furniture, the same you'd expect in a fetish club IRL, then, it's a very niche market. I do have a bunch of Bondage gear and equipment in my runtime, accumulating over the years, but less than 10% of those has really seen itself rendered.
If they are fantasy and/or sci-fi themed, that's a completely different story. Take Davo's sci-fi torture chambers, as an example. Besides the obvious fetish scenes, they can be excellent for any sci-fi horror theme, without the BDSM aspect even hinted in the render.