Erm...
A railcard costs £30 a year, or £70 for three years. If you're paying £17 on the railcard daily, then you're not actually paying for a railcard and you're being scammed!
If you mean the ticket with the discount included is £17 (make sure you're actually add the 16-25 railcard when purchasing the ticket online or a ticket machine), then... yeah, well, the regular price will be (17/2)*3= £25.5, so basically the yearly railcard will pay for itself in literally four days and save you a lot of money in the long run... But of course, if your train journey costs that much, it suggests you have an unhealthily long commute to university and should consider relocating yourself a little closer to university!