the max i have made using amazon aff is $50/mon, using a blog with 250K follower. (i bought it, and the scumbag stole it back.)
the blog has no niche, so the way it worked was basically 'cookie stuffing'. i posted a computer link, but sold a book, for example.
if you have a niche, you can probably do better. since i never had a niche, amazon aff is never my way of moneytizing tumblr.