What are the occasions where you could definitely say that isolating an image definitely helped you sell more than with a background?

Photoshop

I've been wondering the same thing - Photoshop certainly makes it much easier than it used to be - but it still can take a lot of time to fix those little bits of background that aren't automatically removed.

I took a bunch of images of stuff intending to isolate them when Adobe first started accepting pngs, but since I was sick for much of the past couple of years, never got around to isolating and uploading them.  Then it was time to upload Christmas images and I took the easy road and uploaded illustrations that I had drawn in Photoshop on transparent backgrounds for the previous season.

It's hard to compare them to their "on white" counterparts since the images I uploaded the year before were all sets. Whereas, when Adobe started accepting pngs, I uploaded the isolated individual components to Adobe. I've sold sets more than isolated components, but it's really apples to oranges since the sets were online a year longer and offer more components than the pngs. It's also a very small set with a limited Christmas selling season.

I just finished processing a few AI kittens last week - some I isolated as pngs, but the whiskers were really a nightmare since I rarely do any compositing - I'm primarily a travel/editorial photographer and my fine art work is also realistic, so I'm not sure it's worth my time.

I assume most designers who need components can isolate them quickly themselves, but for small business people, bloggers, and art directors/photo editors who are on a deadline, I'd guess isolated components are very attractive. I assume that's why Adobe decided to offer them. And AI can't give you an isolated image so it might be worth the effort.

Like you, I'd be interested to hear how well they are selling for those who've got enough of them online to make a comparison between transparent and white backgrounds. I believe I've read here that they were big sellers on Canva - though I believe they cater more to the do-it-yourselfers than to designers.

this was the microstock question in 2009. For the price is paid today, i dont waste time in this process