Generally speaking, TON Storage is offline and its cost depends on the provider. On the other hand, for TON Cell, you should check the TON Storage fee.
It's important to note that TON Storage only ensures that storage providers don't receive payment if they don't store the file, but it doesn't guarantee that files are actually stored. TON Storage is more about availability than actual storage.
As for the cost of storing data on TON, saving 1 MB of data for one year will cost approximately 6.01 TON. However, it's worth noting that you typically don't need to store large amounts of data on-chain.
If you require decentralized storage, you can consider TON Storage. You can find more information about TON Storage here: https://ton.org/docs/participate/ton-storage/storage-daemon.