On Flow, the cost of storage is directly tied to the amount of Flow tokens an account has. Each Flow account has an associated storage capacity, and the account can use any amount of storage up to its storage capacity without any additional cost.
The minimum amount of FLOW an account can have is 0.001. This minimum is provided by the account creator at account creation and covers the cost of storing up to 100kB of data in perpetuity. If an account holds assets that demand more bytes of storage, the account will need to retain more FLOW tokens to increase the storage amount.
Currently, the amount required to store 100 MB in account storage is 1 Flow token. It's important to note that storing data in an account on Flow doesn't charge tokens from the account, it just makes sure you will keep the tokens as a reserve. Once the storage is freed up you can transfer the Flow tokens.
For more details, you can refer to the Flow documentation on storage fees.