I have v.good academy I spent 15k per week of maintainance costs academy ain't worth that money.
maintainance 15000*4(week)*5(m/SS) =300,000
Now best player i got in v good academy 7/4 ,Can sell around 200k
Please updated to keep the game balanced. 
With all due respect, your analysis is a bit off. To determine the cost of something, you must account for its cost
relative to the next best alternative. For you, the next best (cheaper) alternative is downgrading to a good academy. Thus, the cost of maintaining your very good academy is the difference between maintenance costs of a very good and a good academy, or 7k per week.
Hence:
Very good academy: 15000*4(week)*5(m/SS) = 300,000
Good academy: 15000*4(week)*5(m/SS) = 160,000 Thus, the very good academy costs 140,000, or 87.5%, more per season.
I'd say a 7/x will sell for around 150% more than a 6/x and a 7/4 will sell for around 100% more than a 7/2
Since 150% and 100% are higher than 87.5% difference in maintenance costs, you are clearly getting a better deal with your upgrade.
