For United, beyond Premier League\TV Money, gate money and Champs League money (should they qualify for next season) their big income stream is sponsorship money, and of course starting from next season the £ 75 million deal per year for 10 years they have with Adidas.
With the net £ 120 million they have spent this summer and add in the likelihood\possibility of in Jan and then next summer them spending £ 50 million to make the Falcao deal permanent, probably at least £ 20 million on a central defender (maybe £ 30 million + if they buy 2 defenders) and then maybe £ 60 million on Ronaldo and if they want Kevin Strootman (maybe another £ 30 + million). It is possible they could have spent from this summer just gone to the start of next season at least £ 300 million +.
Add in the high wages of the likes of Di Maria, Falcao and maybe Ronaldo, and that could push that nearer to £ 400 million.
That means of the £ 750 million deal they could have spent well over half of that by the start of next season (before they even have it all).
In addition the Glazers may well use some of that money to reduce debt (another £ 100 million lets say) and should they not qualify for the Champs League next year they could lose £ 20 million from the deal (see link below)
http://www.independent.co.uk/sport/...-to-qualify-for-champions-league-9640856.html
Thus United could have gambled nearly all their Adidas money in the next 18 months.
Oh how good it would be if they failed to qualify for the Champs League for next season and we do !
By next summer they could have a forward line up that includes Falcao (29 years if he is the age he says he is), Van Persie 33 yrs), Rooney (29 yrs), Ronaldo (30 years). Di Maria (27 yrs). Thus in light of recent remarks about Citys' aging squad they may have a core group that are high twenties themselves.
Interesting times if Utds' 'cash splash' fails and Citys' growth continues. The next 2-3 years could indeed cement a real shift of power in Manchester.