Try to remember to include different state taxes as well, some are more than others.
Be careful with shipping etc, I recently looked at a quad, the same quad was available here but after shipping was calculated it was actually cheaper to purchase AU than US even with AU shipping included in the purchase price.
I bought quite a lot when the rates were comparable, but my spending has dropped considerably since our dollar isnt a strong as it was earlier this year and I am much more careful with my purchases.