Penny Lane is in my ears… but in my eyes are the spidery scrawls of countless graffiti pen-wielding tourists on the famous street sign.

Down at the Cavern Club, the cellar arches are instantly recognisable from those thrilling early pictures of the Beatles' first days. And so they should be: the Cavern was faithfully rebuilt from scratch in 1982, down the road from its old location.

The Fab Four have become the Fabricated Four. History's greatest band have become a city's most lucrative brand – a golden goose laying T-shirts and coffee mugs and fridge magnets and 'The Fab 4D, a groovy trip for the whole family.  You'll meet a whole host of magical characters who'll bring the Beatles' music to life in glorious 4D".

It's more stomach-churning than Ob La Di Ob La Da. The Beatles have become so unhip they star in Liverpool's draft ``strategy and destination management plan".

Yes, welcome to Liverpool. This formerly-bleak north-west city has dragged itself from the post-industrial sewer ("it really was a shithole", one former resident confides) and is now an attractive, modern city. Its streets are cleanish and strike an attractive balance between heritage facades and modern interiors. Its docklands, not long since mud and brick desolation, now house decent cafes, an inspired regional branch of the Tate art gallery, and… of course… The Beatles Story, a very slick museum-slash-themepark that climaxes, in a manner entirely unreminiscent of the Day in the Life climax of Sergeant Pepper's, with a "themed Starbucks Coffeehouse, the perfect place to have coffee or lunch".

A recent report by UK Music was unabashed in the pulling power of the Beatles for Liverpool. "Beatles mania has kept Liverpool at the top of music destinations for tourists," the report said. "Liverpool has expanded its tourist offering to translate pop into pounds. Music heritage has created a bed for businesses to take root."

Businesses such as the Hard Day's Night Hotel, a Vegas-style temple of kitsch, where worshippers sometimes throw a tantrum if they end up in a room featuring a poster of the wrong Beatle, where the designers worked closely with lawyers to ensure it was ``inspired" by the Beatles, but not in any copyright-infringing way that might require them to pay money to, say, a Beatle, and where an earnest, capable manager only recently discovered that With a Little Help From My Friends wasn't written by Wet Wet Wet.

Oh they get by with a little help from their friends. In 2012 the Beatles generated an estimated  £70 million for Liverpool's economy.

"Music and The Beatles form the cornerstone of the city's tourist strategy," notes the UK Music report. The annual Beatles Week in August attracts thousands of fans from around the world. Two childhood homes of Paul and John have been bought by the National Trust and restored to an acceptable approximation of their 1950s state (though the childhood home of George Harrison faces demolition).

Pam Wilsher, head of visitor economy development at a Liverpool City business group, said she had assumed Beatles tourism would be a decade-long fad when it began in the 80s. "I'm delighted to have been proved wrong," she said. "When we're at trade fairs the Beatles are extremely useful in making new contacts and breaking down language and cultural barriers."

Some of those making hay even have a genuine connection to the band and its music. Rod Davis played the banjo in The Quarrymen, the skiffle band that John and Paul turned into a rock band. He played with John but was kicked out to make room for Paul. Post-retirement, thanks to Beatles mania, he got the band back together.

"We (four former Quarrymen) still play," Davis says. "Not a lot of gigs a year. Germany, Italy, Spain, Finland, we've been to Russia three times. Japan."

They also make a nice little sideline in Beatles fan conventions appearances.

"When we got back together in 1997 people said 'now you can tell us what really happened' (on the day Paul came to see John play in the Quarrymen, and pop's greatest partnership was born). I said well, I don't even remember seeing the guy there. I went home for me tea."

He doesn't mind featuring in a museum and seeing the Beatles become an industry.

"Well as long as we're not stuffed and mounted here it's all right," he says. And it has its perks - when the Quarrymen need a bit of money they can sell their old instruments, as long as they still have them to dig out.

Another Quarryman, Colin Hanton, took up a career in upholstery when he left the band, shortly before they became the Beatles. He says he drank a lot in those days and reckons if he'd stayed on as the Beatles' drummer he might have done himself some permanent damage.

These days he lives near Penny Lane and sometimes waves at the Magical Mystery Tour bus as it goes past. "Nobody knows who the old man waving at them is," he says. "And look at the fun we're having now."

Martin King, director of the Beatles Story says music is incredibly potent as an attraction. He's seen people shed tears in the attraction's John Lennon White Room.

"People do come to Liverpool partly to pay respect," he says. "It is a quasi-religious pilgrimage that people are on. They're seeking the source. How did it happen? What's in the water?

"We feel obliged to tell the story. When John died in 1980 people started to come (to Liverpool) and didn't have too many places to go. Here we give them the A to Z, the complete story arc."

The Beatles Story has to be in Liverpool, he says. If it were in New York or Melbourne it just wouldn't work.

Is it a shame to talk about them as the Coca-Cola of music, I ask? As just a brand?

"In terms of mass consumption," says King, "they are huge."

"The fact is I sell a lot of T-shirts as a by-product and I probably do sell about £2 million worth of associated merchandise a year, so they are a brand in that regard.

"It's a huge business, it certainly pays for me to bring up my children, put it that way."

But he says he has regular contact with Paul and Ringo. They're real people, after all, and they benefit from the fruits of the music they created.

"If they didn't like what we were doing they could stop us playing the music, stop us showing the images," King says.

And after all, the Beatles industry is just a subset of the music industry. To pretend that the music must be kept pure and separate from the money it generates is to ignore the history of popular music.

And anyway… the Cavern Club is fun, once you've masked the cringe factor with beer, and the cover bands are talented. The Beatles Story is low on cheese and will tell all but the most rabid fan something they didn't know, and the Hard Day's Night Hotel… is definitely there, but you don't have to visit.

And anyway, Liverpool's most popular paid tourist attraction, with more than twice the visitors of the Beatles Story, is a reference to a completely different 60s hit. It's a ferry 'cross the Mersey.