Undoubtedly (at least for me) the answer choices should be between A and E as these are the only two answer choices which talk about cost.
Time saving argument is already established in the passage so we need not be concerned with it, but it is the cost saving argument which we need to establish.
I will not go for E - (not confidently though and here is why)
This is why I would go for E -
E states that the bonus points scheme will be discontinued. This undoubtedly will raise the cost of tickets per person. Earlier, passengers could claim bonus points and get a reduced fare for their trip which they won't be able to do now and hence the tickets will be more expensive for them.
This is why I am sceptical of E -
Reasoning is the same as in A - nowhere is it mentioned whether the train tickets are cheaper than plane tickets.
Agreed that there were benefits of bonus points but the extent of bonus points related price reduction is not established at all.
In fact I think D is the correct choice, so I would pick D
1) Time saving is established in the argument
2) In D cost savings are offered in the shape of added perks (more comfortable ride) which would probably cost more in a plane. Of course we are assuming that the prices of train tickets and plane tickets are comparable.