Bruh, dont. Plant food first. If its really easy to plant moongrass, the price wouldn't high, i expect better explanation next time.
If there's a lot of moongrass, the price will definitely drop overtime. if mc controll how much he will sell it, that means there will be a lot of unused moongrass. Even if mc somehow know how to preserve moongrass, it would take maintenance fee, if mc somehow know how to preserve moongrass without any maintenance fee, that'd be another story.
And, if moongrass something is highly demanded by all people, from noble to commoner the price wouldn't be so high in certain areas since transportation fee is a thing, and i dont see this manhwa universe have any mass transportation to distribute mc goods.
I except better explanation in the next chapter of
What is moongrass
What Mc plan actually is and how he will execute it.