Ask HN: How much would I earn from work at home?

Hi guys.. I am PHP developer working online through Freelancer website http://www.freelancer.com/affiliates/ahmed613/ and I can really tell that I am making enough money according to average income in Egypt..

I am currently making around $1500 to $2000.. and I built a solid network of employers who hire me repeatedly..

But I really need to know.. what is the average income for a PHP developer who work 40 hrs/week online?

I have no doubt that working online is much less than working in real life, because of other costs related to being in a physical workspace.. (although working online has a repeated jobs that you get paid for several times, although you worked on it only once)

So.. can anybody tell me.. how much should I make per month or year, as a PHP developer, according to the American wages and rates?

Thanks guys in advance..