Quite a few people earn that, many people earn more... 5k could be attributed to 167 4free signups per day. Assuming a 0.01% CTR and 1:10 signup rate, you'd only need 167,000 daily visitors - which you can be up to in a week if you post GOOD galleries.
On the other hand, if you don't fancy a huge bandwidth bill,
then I know another way 