We stayed there too and had the same problem (only $50 though) of fabricated cleaning issues. Had the same feeling as you about the people that I rented from.
So, I decided to call the housekeeper that was on the Sloat's list (Call her yourself -- Maria 619-227-8980) and she gave me a long widded story of all the damage that we did (kids wetting beds, candy all over -- total BS). It sounded like a story that was evolving as it was told.
She also told me that it was only recently that the Sloats asked her for detail on over charges.
And I'd note that she's a pretty crappy maid since there were dead bugs & cobwebs when we arrived.
Guessing that this is a situation of someone taking advantage of their client who is 700+ miles away.
John C
Newton, MA