It does depend. I am a little north of Calgary, and I am able to build vacation/sick days (paid) into my fees. So, I charge slightly less than I could get away with charging, but I have Stats off, plus 10 vacation and a max of 4 personal days that I can take with pay. Parents also pay for their sick and vacation days.
If a parent was to ask how I "justify" the fees, I would explain that I charge a flat rate in order for them to hold the SPOT as opposed to a number of hours or days. If I was going to take UNpaid days off, I would charge a higher monthly fee, that would sometimes fluctuate.