There is an obsession because whilst it isn't the be all and end all of how well you're going to do, net spend is a viable indicator as to progress. The clubs with the highest net spend over the past ten-15 years are the clubs consistently at the top of the table. Aside from us breaking the top 4 under Moyes and Leicester the season before last, this is consistently the case. It is an undeniable correlation. Now correlation does not always equal causation, but you can't dismiss net spend out of hand. If you constantly have to sell your best players to buy others, progress will obviously be more limited than it would be if you were able to keep your squad together, culling only the deadwood and adding to your best assets.
I realise that there are examples which do prove that net spend isn't all it's cracked up to be. The RS are the only team in the premier league era to spend over a billion and not win it. Look at the dross united have bought these last few years, and their league position is getting worse every year. Spurs have managed to cement themselves in the top 4 without really spending as big as the others. However the catch up we are playing to those above us is a lot greater than I think people realise. And we don't seem to have a harry Kane coming through anytime soon. We have to be incredibly smart with player recruitment and quite frankly the manager needs to be something special.
The problem we face is highlighted by Man City. Slightly unfair as I know they have the sheikh money, but look what they did this summer. They allowed three fullbacks to all leave on a free, then replaced them all for nearly £150 million. They addressed their weaknesses and spent massively without compromising and losing any key players. In addressing our weaknesses, we've lost our best goal scorer to what we hope will be a rival for a top 6 position, whilst strengthening our goalkeeper and gaining a better centre half. One step forward, one step back. That's what net spend highlights