I think the changes by iStock seems logical. Month over month, year over year, they have been slowly losing market share to Shutterstock. Everyone can read the quarterly filings by Shutterstock, as far as I known, Shutterstock have grown every quarter since going IPO, and probably nearly every quarter pre-IPO. This is just iStock's slow march towards mirroring Shutterstock's business model.

I'm an exclusive on iStock, but I've definitely browsed on Shutterstock. There are some really amazing high quality imagery there. Which are not sold at a premium. So it doesn't make a lot of sense of iStock to have Vetta when something similar can be found at Shutterstock for a whole lot less.

This last past month of sales of August on iStock has been brutal. I've been there many years and I was kind of shocked how bad that month was. I've seen declines, but not like that. I will stay exclusive with iStock for now, because I'm not confident the grass is greener on the independent side. But as the commoditization of stock photos continues to be advance, it is only a matter of time before I drop the crown. I'll see how the sales track for Sep and Oct, then decided if I might be better off on the other side.

My back of the hand calculation of my portfolio and knowledge about my friend's portfolio is that we both average about $0.50 per image per month. Thus 200 images might be the number your looking for. The 20/80 rule definitely holds. Most don't sell, but a few sell well.