My scepticism was a response to a comment claiming not much would be left as profit after these kind of payments. Surely the call for statistics should be aimed at a person making a claim (implicit suggestion that the standard landlord has regular maintenance and repair costs, with poor maintenance and repairs being an aberration) and not the one expressing scepticism at it?
I think it's unlikely there's much statistical data around on % of landlords responding quickly to fix problems. I think I saw once a survey from Living Rent which did ask about repairs, though not as a main focus, but I can't find any results on their website now.
From my own experience as a tenant and stories I've heard from friends/acquaintances, I've heard, apart from things just looking run-down, things like landlords refusing to replace a fridge in a student flat 'because you must have broken it', 1 out of 2 bathrooms being unusable for causing flooding downstairs for at least 8 months, boilers that required constant resetting or they wouldn't heat up the water, thermostats that didn't read the temperature or control it, massive mould just painted over with normal paint. I think these are all things that people would fix in their own houses, but when it comes to tenants living there, aren't bothered.
In fairness you're always less likely to hear about things that are going well.