Take day rates for average/good Java, Ruby on Rails are at around 700+ EUR in Europe and in the US around 900 USD => 900 day rate x 20 days a month x 11 months (one month off for vacation etc) = 198 K
and demand for good Java and Ruby devs is endless ...
I don't know where in Europe you're talking about those 700+ EUR/day but in Spain I've even seem job offers for those same 700+ EUR per month. Yeap, sad but true. Of course, the average is a bit higher. I'd say 18K - 24K/year on average for web developers. So as a freelance you're definitely not going to be making anything close to 700 EUR/day. Maybe 200, if you're good.
We charge a bit upwards of 1000 EUR per day for our senior consultants, here in Stockholm. We have had people who jumped ship and still charge that independently. With 80% workload, that works out to about 220 000 USD a year (With one month off). So it's not completely unheard of for a senior self-employed contrator.
I interviewed most of those people. We couldn't get a decent JS dev for less than 400-450 a day. We could get people, but one (who cost 300/day) actually didn't know much JS.
Take day rates for average/good Java, Ruby on Rails are at around 700+ EUR in Europe and in the US around 900 USD => 900 day rate x 20 days a month x 11 months (one month off for vacation etc) = 198 K
and demand for good Java and Ruby devs is endless ...