Can you explain how this is happening? Are you saying the price we pay for a seat, one of the most expensive in the Championship should be £15 dearer or is this a knock on from the stadium purchase?
I think all El Pres is saying is that the club is losing £8m pa, which TB covers out of his own pocket. There are 23 home league games a season. So, if you do £8m/23/£15, you get an imputed attendance of 23,200, which is not a million miles away from actual attendances.
For sure, one way of covering the £8m loss would be to increase all seat prices by £15 (assuming you think that you'd still sell the same number of seats!). Other ways are to find other sources of revenue or to reduce operating costs. In practice, the club has demonstrated that it is adopting a mixed approach. Besides, they don't need to save the £8m pa immediately, it needs to be reduced to £5m for next season.