It's great that your bill was so low, but there are far too many factors at plan here to know how comperable this is to anyone else's situation.
First, we have no idea how many hours a day your heater runs. Yes we know how many hours you are out there, but that doesn't have a direct 1 to 1 ratio with how long the unit is actually running.
Second, we don't know the construction of your garage and how well insulated it is...there is a vast difference between 2x4 uninsulated walls with exposed rafters compared to 2x6 walls with sprayfoam insulation and R50 in the ceiling.
Third, we don't know what your exterior average temp for the month was. I know you indicated a range, but if the average was 15 degrees it is a huge difference from 0 degrees.
Fourth, we don't know what you set your interior temp to for the times you aren't going to be working or how you might adjust it when you are gone. Maybe you shut it down totally, or maybe you like to keep it above freezing when you aren't out there working.
Fifth, we don't know what your usage of the space is... meaning if you are opening and closing your garage doors several times a day versus this being your working shop where you only enter the passage door and never open the overhead.
Now don't get me wrong - I know this wasn't the point of your original post, but I don't want anyone to get any ideas thinking this means operating a G73 will be cheap. Bottom line, a 5KW heater is a 5KW heater - and if you are paying 6.5 cents per KW, it would cost you 32.5 cents per hour of runtime. Assuming a cycle on/off time of 50% it would cost $3.90 per day to run or $117.00 for 30 days.
You are obviously using your heater much less than 50% of the time, and others might use theirs more... each person just needs to do the math.
BTW - your 6.5 cent cost per KW is likely a winter rate. It will most likely jump back up to 8.3 for the summer when demand is higher.
The only thing I question is why the comment about not wanting to go with natural gas? On a strictly cost per btu perspective, natural gas will always beat electric resistance heating. For some it won't make sense to go natural gas because of the large up front installation costs (running gas lines, installing a vent etc) and in some cases if you aren't using your heater that often you would never recoup the cost, but for those who will use it extensively it is almost always cheaper to go with NG or propane over electric.
I should note I have an electric heater myself - because I don't use it often enough to justify the install costs of the NG unit. I haven't calculated my cost to run the electric only because I don't have the ability to run a separate meter, but I would say my monthly cost is very similar to yours based upon my very limited usage.
Time to get a "hamster" running in a wheel. 