With any site. More images = More Dollars.

On BigStock I have over 2,000 images and never sell less than 50 downloads a month. Fifty cents to sixteen dollars each. Pay out every month. (they do not sell subscription's)

You need at least 250 good images on any site to do anything.

-Larry

Back in the day the minimum number of images needed to start with a (macro) stock agency was 2000 with 100 added each month (generally shot on medium format film).  About 20,000 was consider to be around the point where you could retire.  Not sure how this translates today.   

BigStock for me is really the most awkward site, the less efficient in terms of sales and the one with the strangest "features".

I have a bit over 400 images there and many of them (even if they're from the beginning) are selling really good on the other sites. I submit to SS, FT, DT, 123RF and StockXpert. However, at BigStock I have only 23$ with these many photos. I took a look into my portfolio checked random images and noticed that about 90% of my photos are NEVER viewed. That is, they have ZERO views. Yea well, the preview window doesn't count views, as it is at Fotolia, perhaps. But doesn't matter, because I have tens to hundreds of views at FT and everywhere else.

My opinion: it really IS a problem at BigStock. I don't know which, I don't bother with this site, just wait for those 30$ to come and then remove all my photos. I haven't uploaded there in months and never will again.