With a still pretty new stadium and being located in London, I'm sure a lot of the people visiting to watch matches there aren't even 'plastic' Spurs fans, they might very well just be random people who want to watch a PL game. That's the down side of being in a global city like London which attracts millions of visitors and of course with the Premier League as a league having such global visibility.
But that's been going on at all the London PL clubs as well as the Northwest giants for years now. Could be more of an issue at Spurs because it's still a relatively recent phenomenon. 10 years ago I don't think their global profile was anywhere near where it is now. I don't think any of the big English clubs could be credited with considering the economic means of their local community when setting ticket prices. It's been a wealthy man's (or very fiscally irresponsible man's) game for a while now.