How Transaction Pricing Works

Every extrinsic (transaction) executed on Avail costs a certain amount of AVAIL tokens. These fees vary for different extrinsics and are determined primarily by two considerations:

1. The amount of processing power required to include the transaction in the chain.
2. The amount of storage required to store the transaction on-chain.

Avail's pricing formula is designed to keep transacting on-chain feasible while also making it expensive to spam the network.

1. Base fee: The minimum base amount attached to every single transaction. This is the constant whose current value is currently 0.124 AVAIL.
2. Weight fee: This fee is proportional to the amount of computation required to add the transaction to the network.
3. Length fee: This fee is proportional to the encoded length of the transaction, essentially the amount of space it consumes in the block.
4. Congestion fee: A multiplier applied to the Weight fee based on block fullness of previous blocks (Notice blocks not block, because fee_multiplier is a function of both the current fee multiplier and the fullness of the preceding block. A kind of guard against sudden rise/fall of fee).
5. Tip (optional): This is an optional fee that can be attached to a transaction to incentivize validators.

The formula for the final transaction fee for most transactions looks like this:

Weight fee = [Congestion multiplier * Weight of transaction]
Final fee = Base fee + Length fee + Weight fee  + Tip(optional)

Most transactions like balance transfers and proxy creation have predictable fees — transferring 1 AVAIL requires the same computation as transferring 1000 AVAIL, so the Weight fee stays constant. This changes for transactions that post new data to the network, where the size of the data directly affects the cost. The formula for the final transaction fee for data availability transactions looks like this:

Weight fee = [Congestion multiplier * Weight of transaction]*[submitDataFeeModifier]
Final fee = Base fee + Length fee + Weight fee  + Tip(optional)

submitDataFeeModifier

Posting new data to the chain is a core component of the Avail network. To ensure the fees for doing so remain viable, the submitDataFeeModifier can be adjusted when needed after going through Avail's governance process. This multiplier is used to adjust the Weight fee component of the final fee for all dataAvailability_submitData transactions.

Significance of the data input

For most extrinsics on Avail, the raw size of the input parameters doesn't matter much. DA transactions are different — the size of the data being posted has a direct impact on both fee components: The Length fee scales with the encoded size of the data, since larger submissions consume more block space. The Weight fee also increases because generating KZG commitments for the data requires more computation as the data grows. In short, larger data submissions cost more in both dimensions — storage and compute.

Worked example

Consider a submitData transaction posting a 512-byte data blob under normal network conditions (no congestion):

Base fee:    0.124 AVAIL  (constant)
Length fee:  proportional to ~512 bytes of encoded data
Weight fee:  [1.0 * weight] * submitDataFeeModifier
Tip:         0 (optional)

The exact fee depends on the current submitDataFeeModifier and congestion multiplier, both of which can be queried on-chain. Under low congestion with a neutral modifier, a 512-byte submission typically costs a fraction of an AVAIL token. Larger submissions (e.g. 128 KB) cost proportionally more due to the increased length and commitment generation weight.