Image copyright Paramount Pictures Image caption A scene from US comedy series Frasier

David Brisbane has been a Frasier fan since he first saw the US comedy on TV at the age of 11.

Like many enthusiasts, the 20-year-old wanted to own all of the episodes to watch again, whenever he fancied a chuckle.

He searched on Amazon and found that the DVD box set for all 11 seasons of the show cost £29.99. He then checked the price for the digital download versions of the same shows.

"For one season to download, it cost £14.99. So I did a quick calculation. I would need to spend over £160 to get all of them, which is absurd," he says.

To get all of the shows on a digital download would cost £130 more than buying them all on DVD.

It is not only Frasier where you see such a price differential. BBC Radio 4's You and Yours programme looked at other well-known shows including Breaking Bad, Friends and House of Cards and discovered the DVD box sets are much cheaper than the downloads.

Image copyright Nick Smith Image caption Student Nick Smith was shocked at how much more the electronic versions of films cost

This is a situation that shocked another film fan - student Nick Smith, who was trying to declutter when he recently moved in with his boyfriend.

"We're trying to get two people's stuff into one person's flat. I'm a student - so I can't lose my books, so I've had to move from DVDs to electronic copies," he says.

He was shocked at the price when he tried to find electronic versions of his film collection.

"To buy Mad Max on DVD is about a fiver, but a digital copy is £10 to £12 - that's more than double," he says.

Price gap examples Show/Film DVD cost Download cost Friends series 1-10 £45 £129.99 The West Wing series 1-7 £39.99 £104.93 Breaking Bad series 1-5 £28.71 £53.94 House of Cards series 1-3 £16.99 £44.97 Blue Jasmine £4.92 £7.99

So why is there a price difference? Retail commentator Kate Hardcastle thinks it is a simple case of supply and demand.

"Everything linked to DVDs and CDs - the storage, the players, the drives - all seem to be on the decline in terms of sales. They are on their way out," she says. "People don't want to take up the space in their house."

The British Association for Screen Entertainment, which represents the copyright holders for films and TV programmes, says that prices are competitive.

"The pricing of individual titles and formats varies according to retailers' trading and licensing deals with content owners, but across the board UK consumers have never enjoyed better value for money from their video content," says chief executive Liz Bales. She adds that a new release digital film can be as cheap as £3.49.

A former studio insider told the BBC there could be many reasons why the price would be different. One possibility is that digital video is rarely sold as a package of series at a discount. Compare the cost of an individual series on download and on DVD and the price is very similar.

There are other differences between physical and digital video, the ex-studio executive explained.

"There could be over-supply in the market where the studio has overestimated the number that will sell. Storing product costs money and these days a lot of product is sold on a sale or return basis," he says.

"So rather than accepting stock back to a warehouse, a studio may have done a deal with Amazon to shift the physical stock at a promotional price if it has not sold as well as they had hoped."

Image copyright Thinkstock

It could also be that consumers are paying for convenience. Kate Hardcastle says that young adults do not care about ownership.

"They say they want experiences. If they want to see the next episode right now they are more than willing to pay the price," she says.

Nick Smith thinks the price gap is a farce.

"Almost everything I do in the rest of my life will be done digitally: I work digitally, I do training digitally. It is ridiculous that in this case the physical things are cheaper, when you are paying for a physical form that you do not actually need."

The Entertainment Retailers Association, which represents companies such as Amazon, is also baffled.

Chief executive Kim Bayley says: "The price of video to consumers either digitally or on disc ultimately reflects the prices charged to retailers and digital services by film studios.

"While some disparity may be a result of the timing of release or bundling individual episodes or seasons, it is as much of a mystery to retailers as it is to consumers why digital video with no packaging or storage costs can be more expensive than a DVD or a Blu-ray of the same title."

The association is calling on studios to address the price difference.