I think it's just another attempt at The Guardian's cause to nationalise another industry at the expense of the taxpayer in this wild belief cheaper fares and increased reliability will come around.
Ultimately, you cannot compare the prices in London to the prices elsewhere in the country. London operates completely differently to support otherwise what is an incredibly inefficient and loss-making network. There are several bus routes in London that probably do not make a profit or are even close to breaking even.
The way it has operated for many years is that TfL uses the fare box from London Underground, London Overground, DLR, TfL Rail and London Trams - where these subsidiaries make a healthy profit - to subsidise London Buses. This leaves little money left over for the rail and tube side of the network which is why they're now struggling to properly balance the books and why season tickets will hike every year. It also explains why particularly London Underground has been cash strapped and why purchasing the new Piccadilly line trains was financially difficult for them, with no idea how or when they will be able to also renew the Bakerloo and Central line trains.
Bus operators out of London don't operate routes on a contract most of the time and are entirely on commercial risks and terms. As a result of this, they need the fares to be set appropriately to at the very least break even, but the theory of a firm dictates that they aim for profit. Bus operating costs are high, and particularly if passengers don't use a route as much as the operator anticipates, then you get fares that are a fiver or something like that. Otherwise it is a case of scaling back the route or withdrawing it completely.
I must be right in thinking commercial routes practically make all their income from the fare box, incomes and any subsidies or grants from the local council (if any).
Reliability is something that is obviously down to both internal and external factors. Passengers in London get more reliable services as a result of high investment in technology such as iBus. This allows the controllers to easily see where a bus is on a route and can communicate with the driver in real time to help even out and regulate the service. But that is a system that costs millions of pounds which some smaller independent operators just cannot afford hence service quality and regulation at the worst of times can be really difficult for them. This may be an area where the government could step in to provide grants to have an iBus like system on more bus routes around the country perhaps?
