This is my point - their revenue is generated from the fact that they have the biggest stadium in England, they are the best "brand" in English football and they have more fans than everyone else. This then allows Alex Ferguson to go out and buy the better players.
So its up to the other clubs to (1) Increase their fan base, (2) Improve their brand and (3) Build bigger stadiums to allow their fans to watch them play - yes this takes time and money but Manchester United have been building steadily for years and years now and the more they build the bigger they get.
The rest of the teams need to do the same otherwise they will continually be playing for the title of "the best of the rest". There will always be one team that upsets the applecart every once in a while but at the end of the day it will always be the quality clubs that end up on top.
Manchester United are huge in many parts of the world due to:
1) The Munich disaster
2) David Beckham
3) The fact that they were years ahead of other teams when they became a "brand".
Catching up with them really isn't that simple - they have a 15 year headstart. Chelsea, with all of their titles, players and money aren't half the brand Manchester United are. The ONLY team close is Real Madrid. You cant just "increase the fan base" and "increase the brand" in football. Man U/Real/Barcelona/Liverpool are huge worldwide, you cant just expect Spurs to be able to untrench them.
IMO yes it is unfair. Put a wage cap in the premier league and lets watch Bolton win it!