How are the corners of the ground the same quality as the rest of the ground?
They're the cheap area for a reason.
It comes back to my previous example of peak hour travel vs off-peak. If you travel off-peak it's cheaper, but that doesn't make it a concession, it means you're travelling at a time that is worse to travel at (in the context of a normal 9-5 job that is). If a 10 year old kid and a 28 year old woman are on the same train in off-peak and paying the same rate, neither of them is being provided with a concession to travel. Just because they're paying less than a 34 year old bloke travelling in peak hour does not make it a concession.
When was the last time the corners of the ground were cheaper than the rest of the stands they were in?

In the context of this thread, it;s a rather significant difference.