You think £45 is cheap? Remember that this is £45 for the cheapest seats, where no one really wants to sit - seats that are quarter of a mile away from the pitch.*
Besides, ticket prices are merely a supplemental point. The main issue is simply that Wembley is a soulless and soul destroying place to watch football on a regular basis. Fans are refusing to go any more. They were promised something else; something much better. They were happy to pay a premium for it. Now they are being asked to pay the same premium for the inferior stadium experience that they tolerated last season. It's little wonder that they are consequently picking and choosing. Once Spurs move into the new stadium, demand for tickets will return to normal levels.
* Ahem - possibly a slight exaggeration but, if you've sat towards the top of the third tier at Wembley, you know what I mean!