NEW ? and already upped a ONE year old thread ?
To answer your question: I make around 10 Euros at the most a month these days by playing D3 casual @ 3 hours per day in its end game.
The count is simple: 100-150K per 15 minute run in Act 3. That's 2/2.5 M Gold per day (incl. playing the GAH). That's 15 M Gold per week or 60 M Gold per month.
6 x 1.8 Euro = 10.8 Euro. At launch that was double/triple that amount
So no, it is not something to live from. And I would not play it to earn money, BUT ... like playing poker for 0.25 Euro it beats playing with fake chips.
if you would play it even more casual at 1 hour a day, that would be around 3-4 Euro. Of course I would exclude the "awesome one time ever hit the jackpot item", but this is just the basic coverage of gold farming without miracles.