EC1, if you take your argument to its logical conclusion, then you do away with spectator sport altogether.
There will always be a premium to watch top-end sport live at the venue (doesn't matter if it's the Festival, Wimbledon or the World Cup Final) and sitting opposite a hi-def telly is almost always going to give you a better view.
In fact, you can make exactly the same thing about Glasto, T in the Park and other music festivals too.
Or Crufts.
Generally people don't attend 'an event' for the view - they're motivated by other factors that cannot be replicated by sitting in front of a TV, dressed in bri-nylon, picking at your dandruff whilst they switch to Sedgefield.
I would not hesitate to recommend a visit to the Cheltenham Festival to anyone.