Love railcards.
I visit home (or used to) twice a year: once at Christmas, once in Summer, and the tickets (a return) would run for around £50. That's 100 a year in costs just from that, for 3 years that's 300, and saving 33% saves me 100. the card is £70 so thats a 30 saving.
But I used rail for a lot more (local travel, visiting places, going to London/Inverness/Mallaig/Oban/god-knows-how-many-other-places
Tbf the railcard has probably saved me at least a few hundred in travel costs.