If the Magic Plant is appearing in your nursery, you don't need to worry about it. That particular Magic Plant's effects aren't crucial to what the customers perceive, and you can set the prices however you like. Borg's breeding reference tells you what those prices are, and you can usually command a higher price than that, anyway.

As far as editing your savegame file, that's not something we will discuss here. Justifiable or not, people would inevitably use the information to cheat.