This question has been asked before, just worded slightly differently.
Restitution must be related to the consequences of the criminal action. They cannot be speculative and must be calculable. There may be future restitution to compensate for future damages consequential form the criminal acts.
Prosecutors are bound by ethical standards applicable to all lawyers. In your state, there may be judicial officer standards as well.
I am a little cautious in answering because it is hard to know what the prosecutor is basing their decision on. But, as long as the prosecutor is not abusing their position, they can ask for the restitution they deem appropriate. The JUDGE is a safe guard and your attorney can ask the judge to modify the plea agreement if it is infact unfair.