Your transfer prices doesn't make sense at all. You are talking about 170M for Coutinho, where did you get that? Semedo was 30 fixed, Dembele is reported 120 + 30. Those add ons count for multiple years and it's not even know what the details are and if they will needed to be payed. Taken over a 4 years term, it's not alot.
That makes it:
Semedo 30
Marlon 5
Deulofeu 12
Paulinho 40 (reports suggest 32 with 8M payed by himself, not sure if true or not so let's count 40)
Dembele 120
Coutinho 120 (unknow but will be similar to dembele probably)
Total = 327M
- 222 Neymar = 105M
And 1-2 players will probably leave if both Dembele and Coutinho come.
Dembele is really not getting a world class player wage yet, he didn't earn that much at dortmund either. Coutinho is reportedly willing to take a wage cut to join his dream team also.
Well, if Dembele is 120+30, that means that we will probably pay 120m now and 30 in the next 2-4 years, based on variables.
Now, if you count only 120m for Dembele into this year and 30m into upcoming years, then you have to add addons from previous years into a current year.
For example, we are probably currently paying addons for Umtiti, Mats, Rakitic, Suarez, Denis, Gomes, Paco etc
Majority of them had some addons in terms of trophies, games played, goals scored etc
So, you can't say: it is 300m now and 120m in the future.
Fine, but then you have 300m now, 120 in the future, and probably 50-ish m in addons this summer from previous transfers.
So, it evens out to some extent and it is again way higher than only 300 for fixed amounts from this summer.