Last year I travelled from Liverpool to London and bought the tickets the same day. The were quite expensive, and would apparently have been much cheaper if I bought them a day or two before.

Now, I will visit Brighton, and travel there from Gatwick airport. Does the same apply here?

The reason I ask this is because it is quite short route (30 - 40 minutes), and the type of travel seems like a more regular airport transfer than the Liverpool - London trip.

I did do some research, trainline says:

Buying in advance can help you save up to 43% vs. a walk-up fare on the day of travel. Buy tickets below with Trainline – the UK’s largest independent ticket retailer.

This doesn't really say that these tickets in particular will be more expensive.

The Gatwick airport homepage doesn't have any information about pricing at all, and no advice that tickets should be purchased beforehand.

So what can I expect? Will my tickets be more expensive if I purchase them after my arrival at the airport?

Last year I travelled from Liverpool to London and bought the tickets the same day. They were quite expensive, and would apparently have been much cheaper if I had bought them a day or two before.

Now, I will visit Brighton, and travel there from Gatwick airport. Does the same apply here?

The reason I ask this is because it is quite a short route (30 - 40 minutes), and the type of travel seems like a more regular airport transfer than the Liverpool - London trip.

I did do some research, trainline says:

Buying in advance can help you save up to 43% vs. a walk-up fare on the day of travel. Buy tickets below with Trainline – the UK’s largest independent ticket retailer.

This doesn't really say that these tickets in particular will be more expensive.

The Gatwick airport homepage doesn't have any information about pricing at all, and no advice that tickets should be purchased beforehand.

So what can I expect? Will my tickets be more expensive if I purchase them after my arrival at the airport?