I'm reading docs on Venom and they said that the problem on using mapping in ERC20 contract is "Now let's imagine that we have an erc-20 like mem-token contract with one large hashmap of token holders. Everyone who has ever bought this token will be recorded in this contract. Eventually, we will have a situation where users with large balances will have to pay for the storage of those who have only pennies left on their accounts."
I understand is that if mapping get bigger then access mapping will cost more gas ? But i think it is not true because access and storage have same gas. Anyone can explain me why they said that? Thanks for your time