Did you buy your insulation yet? If not, consider doing a lower R-value insualation. I found some insulation energy savings calculators online. I was surprised by the calculations.
I am insulating my 3200 sq ft shop for R-11 it is going to cost just under $1200 from a local wholesale building material supplier (I am not a contractor, but they will still sell direct). According to the calculators, I will see a $2800 savings in energy costs each year.
The minimum recommended insulation for my area is R-19 in the walls and R-30 in the ceiling, but most builders will double that. When you rerun the calculator with R-19 walls and R-30 ceilling, the payback for the increased cost will take 30+ years.
I am convinced insulation sales are really a gimmick. There is definitely a point when your return on investment is terrible, it is a much lower R-value than they lead you to believe. I know several people that have spent $1000 or more on increasing insulation in their homes to later their energy savings are only $1-$2/month.