Difference of the art unzipped maybe 500 bytes but the difference gzipped is only 150 bytes.

Also this argument of comparing home internet bandwidth overage is only valid if you are serving a site like this from your home :) If you think you're going to get impacted by this overage because of your surfing habits, you'd have to surf...

1GB/150= 6 666 666 pages in the month

since there are 2 592 000 seconds in a month, you're looking at 2.5 page loads per second. You're probably not there.

Also the main page load is 1.5M (including all the resources) so the 150 bytes is even less of a burden.

I think you'd be better off looking at optimizing/saving money somewhere else ;)