The US's IRS estimates the cost of driving at 57.5 cents a mile. But that's with US fuel costs, insurance rates, and depreciation curves. I know gas in Europe can cost 2x as much as the US.
Assuming 50 work weeks in a year (standard in the US), that's 180 mi/day * 5 day/wk * 50 wk = 45000 miles driven.
Which comes out to $25,875/year.
As a result of all this driving, you're earning an extra $3500/mo = $42,000/year.
So financially, assuming the IRS figure is accurate, you're earning an extra $16125 for an extra 750 hours of driving time (assumes you're driving at 60mph the entire time, which is probably faster than your true average speed), or an extra "hourly pay" of $21.50/hr.
That sounds terrible to me for driving that much every work day.
Now of course, the IRS estimated cost of driving was $25,875/yr, and your estimated cost was $8400/yr. I know for a fact that the majority of this IRS cost estimate is depreciation. Which is highly nonlinear - a high mileage car will experience very little depreciation compared to a low mileage one. Plus, not knowing where you live, the cost of gas may be very different.
How did you arrive at the $700/month in associated extra expenses from driving and possibly staying overnight? It seems like something worth examining.