Amazon charges $0.1 for 1GB storage. suppose one active user uploads 5 pictures each day on average and each picture takes up 1mb. If you have 500k active users, they can use up 500k x 5mb = 2500GB = $250.

$250 x 30 = $7500

because this cost is accumulative, within a year, the monthly bill will be as high as $75000. This is just the data storage. There are extra fees for database access, bandwidth ...