As the Dexi sensors last more than double the length of time than the Libre the Dex is still far cheaper
And I think this is where definitions come in to play. The upfront cost of the Dexcom is ~£1200. The upfront cost of the Libre is ~£138. The affordability of the Libre is therefore far superior to that of the Dexcom.
The long term running costs of the Dexcom are lower as long as you can get four weeks out of a sensor. On a month by month basis, you will pay £100 per month for Libre, and you may pay £58 per month for the Dexcom.
Over the first twelve months, assuming the 1 month sensor life, the Dexcom works out at the upfront cost plus 2x Sensor packs (4x Sensors) at £256 per pack. So your first twelve month cost is £1712.
For the first twelve months with the Libre, you will pay for the starter pack (£138) plus the sensor at £48 per sensor every two weeks. This works out at £1290.
Going into your second year, the annual cost of the Libre is £1248.
The Dexcom is £768 (assuming the month per sensor). You may, however need to add an additional transmitter in the second year with the Dexcom once the battery is dead. If you do, that will set you back a further £300, making the Dexcom roughly 85% of the cost of Libre over the second year.
Over the two year period, then, it seems that the overall cost of the Dexcom is between £2480 and £2780. The overall cost of the Libre is £2538.
There are obviously some significant assumptions around Transmitter and Sensor life on the Dexcom in this calculation, but the point I am making is that in reality they are much closer in total cost than many people think, and the key difference is really affordability and perception of affordability.
It is much easier to fork out £138 up front than £1200 upfront, and then to maintain a habit in £48 or £96 chunks than in £256 chunks.