Those earnings are impressive.It ain't easy. But I sold my old photo web site - irishviews.com a year ago.
Here's some info about what I made and how I made it up until I sold it :-
How To Make £20,000 From Some Average Photos & The Google Display Network (AdSense)… :: Google Adwords Northern Ireland, Belfast & Newtownards – Pay Per Click Consultants
The old site was hand coded html and was getting to be a right pain to update, so it had to go.
I've since started a new wordpress based photo web site - photos-for-you.com which is a hell of a lot easier to update, but so far my best month has seen AdSense earnings of around £22 (after about 1,000,000 hours of effort being put into it).
I was in 2 minds about whether to bother with a new photo web site. Put it this way - if I didn't enjoy taking photos I wouldn't be doing it. It's still nice to get regular payments into your bank account without having to deal with customers all the same...