But the cost to Bell and British Telecom was not £2 per minute, or £1 per minute, or even 1p per minute, it was nothing at all. Their costs were not for the call, but for the infrastructure over which the call was delivered, a transatlantic cable. If there was one call for ten minutes, once a week essentially at random, that cable must still exist, but if there are 10 thousand call minutes per week, a thousand times more, it's the same cable.

So the big telcos all just picked a number and understood it as basically free income. If everybody agrees this call costs £2 then it costs £2 right, and those 10 thousand call minutes generate a Million pound annual income.

It's maybe easier for Americans to understand if you tell them that outside the US the local telephone calls cost money back then. Why were your calls free? Because why not, the decision to charge for the calls is arbitrary, the calls don't actually cost anything, but you will need to charge somehow to recoup the maintenance costs. In the US the long distance calls were more expensive to make up for this for a time, today it's all absorbed in a monthly access fee on most plans.