I had thought that since both [Loco2](https://loco2.com/) and [Capitaine Train](https://www.capitainetrain.com/welcome/512fcc) have agreements with SNCF to sell domestic French train tickets (amongst others). However, I've noticed that sometimes the prices between them can vary a lot. Is there a reason for this?

As an example, Lille to Agen at 10:11 on Saturday 14th June, Loco2 want £101 (= €124.82), while Capitaine Train only want €111.10 (= £89.90)
![Loco2 prices](https://i.stack.imgur.com/uteC7.png)
![CT prices](https://i.stack.imgur.com/ALI3T.png)

On the other hand, Lille to Tours at 08:42 on Saturday 5th July, Loco2 only want £46.50 (= €57.47), while Capitaine Train comes in at €89.70 (= £72.58)
![Loco2 prices](https://i.stack.imgur.com/x3gEe.png)
![CT prices](https://i.stack.imgur.com/cWAXY.png)

Given that they are in theory reselling the same tickets, how come they have different prices? And is there any way to know in advance which is likely to be cheapest when there is a difference?