I don’t live on “this fine island”, although some of my distant ancestors may have lived there. I’m not sure it’s necessary to live there, to address your question. Just as I am sure there is no definitive answer to your question. Keeping in mind I took economics in first year, about 40 years ago, and hated the class, let me throw out some ideas. Take what you want from them.
We both live in mostly free economies. Here we have a Milk Marketing Board and a Wheat Marketing Board, and the government dictates what many doctors can charge for services. Most other businesses are free to charge what they like. Usually, what they like is a price that delivers some profit and which people are willing to pay.
Generally people want to pay less and businesses want to charge more. There are exceptions though. There was a great restaurant across the road from where I lived for a few years. They were only open a couple of days a week, and only for dinner. The food was fantastic and relatively inexpensive. The business was a make work project for someone’s child and no one cared if they made a profit. Years before that, at Main and Benlamond, there was a marine store — they sold boats and motors though they were many blocks from the lake. They were in business for years, until the owner retired, but they were expensive compared to the Canadian Tire a few blocks up the street. One time, probably when 10 or 11 years old, I asked why they were more expensive. The answer was that at their prices they got some customers and if they charged less they would have to work harder. So, some people found a reason to pay.
As a photographer, you are more like a manufacturer or service than a retailer.
Looking at retail for a moment anyway, Target is a US brand that came to Canada a couple of years ago, and now they are leaving. For Target, Canada has been a huge money pit. Target is a successful US store and many Canadians skip across the border, at places like Buffalo, to shop at Target because there are products not generally available in Canada, at lower prices. There was a lot of anticipation when Target announced they were opening Canadian stores. Unfortunately for Target the anticipation dissipated as soon as customers entered the Canadian stores. Prices were the same, or very close to prices at other local stores, and selection was also very similar to other local stores. On at least two occasions I wandered through a local Target store, and left empty handed. I never saw anything I wanted to purchase. Living two hours from the border, I have never felt it was worth the drive to shop in the US, but others have, and they report the US Target stores are quite different to the Canadian stores. So a lesson might be that you have to either manage or meet expectations.
Manufacturers usually figure out how much it costs to produce and market an item, then they add some profit and that becomes the price. It is a little more complicated than that because they also have to guess the number of units they will sell and amortize development costs. It is then up to someone to purchase the goods. Sometimes the product is so desirable that supply cannot meet demand and the price can rise. Sometimes there is no demand and the company loses money. Services are similar although the product may be less tangible so the inner workings are more difficult to see. If you ask for a quote to have custom software written, and you decide the price is too high, the software is not written. Some negotiation could take place, extra features added, or the price lowered. Or not, depending on how desperate the developer is for work.
So, a long way to say that your photo has no value if no one is willing to pay you for it. And it may have a lot of value if someone wants/needs it enough to pay a lot for it. It may have less value if someone else is willing to provide a similar photo for less money.
Back in the days of film, someone could spend a lot of money on gear and processing without ever figuring out how to create an advertising worthy frame. Now you can spend a few hundred dollars on a digital camera that will deliver reasonable photos if you just aim and press a button. Also, there is all kinds of help on the Internet. YouTube is full of how to videos. And, you can access millions (billions?) of stock photos from your desk. Stock may not help if you need a specific photo, of course. The cheap camera with basic operator may not help if you need exact colour, good light, good pose, precise exposure, etc. How much better are your photos than those she can take on her own, or obtain from another source?
Some blogs make a lot of money, well into six figures if they have a large following and good advertising contracts. How much will your photos boost popularity of the blog, or retain existing visitors?
How much value? That depends on your photo skills, your marketing skills, your negotiating skills, and your salesmanship. I have no idea.