I do a small community church trad, 8 windows about 6'x2' and about 10 windows 4'x4.' I charge £15 and do them about 6 times a year and the same for insides which I do about 4 times a year, takes about 30 mins outside and 45 mins insides as I have to occasionally move chairs to get at windows, It's quite a nice job as I just turn up when I think it's about time for them to be done. These are also bad wooden framed, with putty falling out.
I've also got some lucrative gutter clearing work as well so think it's a reasonable amount.
You may also get additional work from congregation if you can leave a card somewhere.