Why are London rents so unpredicatble for the same type of property?

[mashwith]

We rent a one bedroom flat in Paddington for £1,850 a month. It's about 50 sqm in a smart period building. Friends around the corner live in a similar flat but it's 38sqm and the rent is £2,200. Other friends live in Balham, their flat is 45sqm but has a small patio and the rent is £2,500!

So why is it that rents in London no longer make much sense? Twenty years ago there used to be a big difference between rent in Zone 1 and Zone 3. Now they seem to be very similar. Even ten years ago rents for flats of the same spec all cost around the same. Now there can easily be a £500 difference per month for the same flat. That's a huge amount of money to be overpaying.

Rents are up to the landlord and some are chancers.

Can't answer re London specifics, but where I have looked a whole host went on the market in May or June then got reduced by as much as 25% in the first or second of weeks of July when they had not been rented. Some were reduced by as much as £600 pm.

Time of year seems to matter re: what LL's think they can get and I think some strategically time advertising to when most people are likely to be looking.

Zone 2/3 but closer to tube station, might be more convenient than Zone 1 but not close to tube station?