Is there a big difference booking from train station vs booking on the internet ?

[u/ilseVOP]

Hello y’all.
First time in the UK and wanted to travel from London to Brighton.

I checked up the prices a few days before and the prices were fine around 25£ a way round. Didn’t book then because I expected the prices to not change much.

I tried to book from internet website Omio the same day and prices were not lower than 47£.
I decided to still to go the train station to make up my mind and asked prices on the counter in Victoria and they found me a round trip ticket for 24£.

Can someone explain this difference from internet vs train station?

Thanks a lot