http://www.tech-faq.com/proxy.shtml earned $707.23 from AdSense in May. That data is from Google Analytics. In the same month, it earned $552.16 from submission fees.
I am tracking my other proxy lists using URL channels in the AdSense portal. Here is a sanitized report from May showing the data Google will allow me to share.
The proxy niche is very competitive and has poor revenue potential. But, it's fun and I really dislike censorship.