Not always but most of the time it does.
Spurs net spend was 16th in the summer. We were 2nd. You simply can't use their squad and dependence on one player to justify ours.
Position does matter. Like it or not strikers are the biggest difference makers. It's why they cost so much. You'll always miss your star striker more than you will your star midfielder.
I think it's yourself who has forgotten context. For the last five years we've been spending on par with the biggest clubs in the world. That's been the case under Mourinho. But you and others are using a Spurs comparison to justify a complete reliance on one player. Why not compare the importance of one player with the other giant clubs?
Spending is just one factor. Why not have a look at who we bought, how much for and where they are now?
13/14:
Fellaini (27m): Good signing
Mata (36m): Good signing
14/15:
Shaw (30m): Rubbish - will be sold soon
Herrera (28m): Very good signing
di Maria (60m): Sold not even 12 months later
Rojo (16m): Good signing
Blind (14m): Very good signing
15/16:
Depay (28m): Sold
Schneiderlin (25m): Sold
Schweinsteiger (6m): Sold
Darmian (13m): Good signing
Romero (free): Very good signing
Martial (36m): Very good signing
16/17:
Mkhi (27m): Good signing
Bailly (30m): Very good signing
Ibra (free): Very good signing
Pogba (89m): Our best player
17/18:
Lukaku (75m): Very good signing
Matic (40m): Very good signing
Lindelof (30m): Not sure
Context is the fact that we've signed 22 players (including Falcao loan) which is two starting XIs and have kept 14; with only 7 of them being consistent starters over the last season and a half.
Numbers are based on memory (so feel free to correct me) but we've spent nearly £600 million since Fergie retired and have received around £90 million for those sold (from the above). We've continuously changed our backbone (consistent starters) over the last 4 years:
13/14: Rio, Evans, Smalling, Vidic, Carrick, Cleverley, Valencia, Welbeck, Rooney
14/15: Smalling, Blind, Carrick, Valencia, Mata, Rooney
15/16: Smalling, Jones, Valencia, Carrick, Blind, Herrera, Mata, Rooney, Martial
16/17: Bailly, Jones, Rojo, Valencia, Blind, Herrera, Pogba, Mata, Rashford, Ibra
17/18: Smalling, Valencia, Matic, Mkhi, Rashford, Lukaku
There's hardly any consistency in our starting XIs since 2013 with massive changes every year, yet you're assuming that because we've simply spent X amount we should be up there with the elite. No, it doesn't work like that and especially not for a team that went from winning the league to:
Getting smashed at home by Liverpool and City, allowing teams like Newcastle, WBA, Everton to record wins at OT for the first time in 20+ years.
A team that bought "Gaalaticos" yet never started them and marginally finished 4th.
A team that, somehow regressed again, could barely muster a shot on target against the mighty Sheffield United, relied on an 18 and 19 year old to carry them to 5th and an FA Cup win. Not forgetting that we scored 49 fecking goals in a season - worse than Moyes' United.
A team that finally stopped getting embarrassed at OT by the so called minnows of the league, won two trophies and got it self back into the CL.
Now is a team that has made OT into a fortress (36? games unbeaten at home), is dominating its CL group, will find itself in the SF of a domestic cup and sits second in the league.
That's context. Not just we spent money, we should be winning the league which is all you seem to want to consider.