How they build this website?

On Heathrow Taxi | Gatwick Taxi | Gatwick Taxi Cab Transfer | Heathrow Taxi Cab Transfer I’m curious how they build the form from the first page.
To they have a list in both parts (start and finish) with all miles and prices?
Or the site is connecting to google maps wich is taking the start point and the finish one and return the miles so they can multiply this with the the cost per one mile and gives you the result?

Looks to me as if they set prices between each destination by hand.

They may well have plotted each centroid of a postcode to start off with, to get an idea of distance - but distance is not the sole indicator of price - it has to take into account time.

Oddly, it does not seem to work add more for rush-hour work, or weekends - so I’d say this was less sophisticated than you imagine.

When i tried to book between two postcode areas (ie not to or from a port or airport) it quoted me £0.00 - which seems a good deal.

In london almost every minicab company takes your money depending how many miles are from where you are to where you go. If you are in the area of that company the price per mile is £2-3. If you will take a Black Cab you will see a red counter that is zero when you start and after each mile will increase.
If the code is build by hand there are a lot of combinations. That wasn’t a complete form like this one.
In the last one you have options for postcode, address, hotel, airport, etc. So you have to compare each street with each street, then each street with each postcode, then each street with each hotel, etc. That’s a lot of work. Am I right?

yes