Ticket agency as I thought - the big money for Ireland vs England is that most feel this will be a deciding fixture for the Title/Grand Slam/Triple Crown. Though I suspect ticket prices will change towards the end of the tournament...
Also if you look at the top of the page in smaller print (funnily enough): -
"We are a secondary ticket agent. Tickets sold on this website are above the face value. Prices may change nearer the time of the event."
Exactly why I picked Chelsea as an example - though I guess there's a big difference in pricing even within the Premier League itself?

