It is 200m on 5 years, but 2 years of playing and 3 years of retirement.
So, at the end of the day, we are still paying 100m wages for a 34/35 and 35/36 years old Messi.
Imagine a season 2022/23 when Messi will be nearly 36 in the spring and we will be paying 100m for his services.
Your maths about 5 years is wrong.
Unless if you think that in 5 seasons from now in 2025/26 season, when Messi will be 38 at the beginning of a season and 39 at the end of a season, he will still play football and that we will be paying 40m per year for a 39 years old player.
About us having a shot at La Liga, in some other thread I posted trends where we are winning less and less points in each new season (dropping from 90+ to 80-ish lately) and scoring from 110-ish to 85 lately.
Again, unless if you think that our team will suddenly improve (why would it?), we aren't winning anything unless if both AM and RM will win 80-ish points.