YANBU. I've twice had either the landlord or the cleaner try to extort money from me for extra cleaning or "damages". The first time I was young and stupid enough to just pay up. The second time, I disputed it and they backed down.
NB I should also say that I've rented lots of holiday properties in my time and most landlords and cleaners have been lovely and no problem at all. But there's always a few bad eggs...
Most recently we rented a holiday flat with friends last year. Me, DH and baby were the last to depart so I know exactly how it was left. (Clean, tidy, with the sheets and towels stripped and left in a pile for washing.) The rental for the week included a small fee for contract cleaners to come in for an hour at the end of the week. Considering this, we left it super tidy.
We got a call from the agents a day later saying that the cleaning agency used by the landlord were demanding extra money for cleaning because we'd left it in such a state! We categorically refused and recommended that the landlord should also refuse to pay. The cleaners were lying and untrustworthy. The agent and landlord were both persuaded of our version of events and our deposit was returned in full.
The first time was years ago on my first holiday after I graduated so I was around 21. A group of us rented a cottage with my much younger brother (then only 13).
Me, DB and exBF and a very shy ex schoolfriend were the last to leave and the landlord (a local farmer) and his cleaner (a lady who was evidently his friend) turned up while we were still waiting outside the property for a taxi which never turned up. They both looked like very normal, respectable middle-aged people and we'd left the place clean and tidy so didn't expect any trouble. The only thing which wasn't strictly in keeping with the cottage rules was leaving some food in the fridge. This was because there was more food left than we could carry and I couldn't bear to throw away good butter, cheese and eggs etc.. that I thought the cleaning staff might be able to take for themselves (having once worked as a cleaner in an apartment hotel and been very appreciative of this kind of thing).
Anyway, the two of them shouted and screamed at us, called us names, accused us of having parties and too many people in the cottage, claimed that the bathroom was "drenched" because there were a few spots of water on the floor near the basin. I was totally shocked, my friend was nearly in tears, exBF wasn't any help, and I just wanted to get my little brother away from those people so I just handed them the extra money and walked off with our big bags.
I'm very careful with rentals now and stand my ground on principle.