Looking through Forbes' valuation of the 32 NFL teams, I noticed Buffalo is third with $59/fan. Only New Orleans ($77/fan) and Green Bay ($277/fan) were higher (and I'd argue Green Bay is a special case).
So, if Bills fans really are more passionate than average, and if Bills fans are unusually committed and unusually demanding, here's something of an economic justification (money is a measure).
The stat also indicates that Bills fans are especially important to the team. The New York teams can afford to lose some of their $8 fans, but not the Bills! And that's why sites like this are so important.
So while I wouldn't draw too much into this little Forbes stat, I do think it says something about our unique fan base, and even gives us a little psychological leverage at the imaginary bargaining table with ownership and management, where we gripe and moan and -- hopefully one day -- raise a glass together in celebration.