Seeing as Spurs have finished above United in 2 of the last 3 seasons, your claim lacks credibility.
It would be more true to say that some United fans are seeking reassurance that they can still mix it with the big boys, despite having dropped down into the EL. Hence their celebrating a world record fee for Pogba (as if paying so much money was something to be proud of), their constant references to club income and the obsession with signing big name players like di Maria, Schweinsteiger, Ibrahimovich and so on.
As for the rest, Spurs net spend during the Prem era is barely above Sunderland's, and this despite the fact that Spurs have been in the Prem the entire time whilst Sunderland have not.
Nor am I "crying poverty" ... in fact I'm very happy that the club is investing its money in a new stadium complex, in further development of our training centre, and in youth development.