Are those the only figures you're questioning?
The point was to look at fairly optimistic costs to maximise the number of miles available to do with the goal to be that any questions over values given to be that I'd say the values too low, if you start adding an extra £100 to something, based on 12p per mile you lop 835 miles from the distance you can travel. Which in turn makes
In the three points you make.
VED is only a flat rate on newer cars, some cars still have rates under £50.
Main dealer rates can be that high, but some individuals can (still) undertake a service themselves and then pay for an MOT.
Yes, the car would have to be very cheap, and you be very lucky to not have anything go wrong or need to replace something expensive - like the cam belt.
As I was saying very few people would be able to run a car for half the average cost of car ownership, as you point out, it's also easy to double those values.
As to the £3,600, that's based on a range of £280 to £300 per month and using the higher figure.
One website which uses the lower figure gives the following rundown:
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www.nimblefins.co.uk
Purchase/Depreciation per year £1,251
Petrol and Diesel £747
Car Insurance £621
Repairs and Servicing £473
Motor vehicle road tax £153
Parking fees, tolls, and permits (excluding motoring fines) £39
Garage rent, other costs (excluding fines), car washing, etc. £44
Motoring organisation subscription (eg AA and RAC) £19
Anti-freeze, battery water, cleaning materials £10
Motoring fines £0
Annual running costs for a car £3,357