I tried to defog my own windows at home, and I am now convinced that these window clearing services are a rip-off.
Drilling the holes requires a diamond drill bit and patience. However, even after a couple of weeks it didn't change the appearance of the fog, in either the badly fogged or the minimally fogged test window I chose.
Tried filling windows with vinegar and soaking overnight before draining. Didn't work, so I tried Calcium Lime Rust remover the same way. Didn't work.
Tried taking glass out and cutting the seal. The minerals inside were rock-hard. Using a razor scraper and CLR, I was able to clear about 10" by 10" of window pane in about half an hour. Mind you, that is on only one of the two panes of the 17" byt 22" double paned window. Quick arithmetic told me that the value of my time was worth much more than the $60 per window I had been quoted to replace the glass.
I am now enjoying my newly-installed clear windows!