He was under the assumption that he could dump all the materials, but he forgot that even the characters did not have unlimited money when it came to transactions with Players.
It was probably in order to keep a balance. Whenever the world's next phase began, he was given a moderate amount of money, just enough to sustain and stimulate his career.
However, in all of his previous lives, his economy thrived quite well since both Players and normal residents came to ask him for potions. Since he was restricted to his store, he couldn't go out and spend the income he earned.
Buying things from merchants was the only way he kept on surviving. Other than eating, he realized that he didn't really spend much money in comparison to ones he gained.
The materials he brought, especially the Crystal Rabbit's parts, were priced at a threshold that a beginner butcher store won't be able to pay off.