Our previous post discussed how shared blob aggregation optimizes Ethereum's blob space by combining DA requirements. Today, we dive deeper into a critical piece of that efficiency puzzle: how to price aggregated blob transactions fairly and effectively.

Understanding Blob Aggregation

Blob aggregation intelligently packs multiple Ethereum transactions into a compact, space-efficient unit—potentially spanning multiple blobs.

Ethereum’s blob space is limited. Competing transactions need to be packed in a way that maximizes utilization. Blob aggregation helps by grouping transactions to reduce overall gas costs, with additional savings from amortizing base costs across the group.

Think of it like a version of the “knapsack problem”—how do we fit a set of transactions into limited blob space while maximizing efficiency and minimizing cost?

How Blob Transactions Are Priced

Blob transactions consist of three fee components:

Blob Base Fee
Transaction Base Fee
Priority Fee

The first two are set by the Ethereum network. Only the Priority Fee is user-defined, making it the key mechanism for signaling urgency and inclusion preference.

The Core Pricing Dilemma in Aggregated Blobs

What happens when different transactions in an aggregated blob have varying willingness to pay? How do we fairly divide the shared cost of the blob space?

Enter Shapley Values - a concept from cooperative game theory used to distribute costs (or rewards) fairly among participants based on their marginal contribution to the group.

Our Pricing Approach at Spire

At Spire, we are exploring ways to dynamically price blob usage and transaction costs, then calculate each transaction's marginal utilization. This results in a pricing model where:

You always pay less than you would in isolation
Costs are distributed fairly based on declared willingness to pay and actual usage
Fast inclusion is guaranteed by setting the group’s priority fee to match the highest participant’s

The result is a system optimized for maximum inclusion and minimal latency, without undercharging smaller contributors.

Benefits of Fair Aggregation Pricing

Fair and efficient blob pricing enables:

✅ Reduced transaction costs by sharing gas across many participants
✅ Fairer pricing mechanisms using transparent, marginal-impact-based calculations
✅ Fast inclusion for lower-fee users, and cheaper fees for higher-fee ones

As we continue to iterate, we aim to improve fairness and efficiency to support long-term scalability and economic sustainability.

📊 Example: Shapley Value Cost Allocation

Let’s walk through a simplified example (excluding Blob Base Fee and Transaction Base Fee for clarity):

Transaction A

Priority Fee: 2 wei
Uses 50% of a blob
Standalone gas cost: 42,000 wei

Transaction B

Priority Fee: 1 wei
Uses 50% of a blob
Standalone gas cost: 21,000 wei

If included together, the total cost remains 42,000 wei, thanks to shared intrinsic gas savings.

To calculate Shapley Values, we look at all possible orderings in which transactions could be added and compute each transaction's marginal contribution to the total cost. We then average those contributions across all permutations. This ensures each participant pays an amount that reflects their impact on the collective cost.

Using Shapley Value cost sharing we allocate costs as:

Transaction A pays: 31,500 wei
Transaction B pays: 10,500 wei
Total: 42,000 wei

📈 Outcome: Both users pay less than they would individually, while still benefiting from top-priority inclusion. Efficiency meets fairness.

Looking Ahead

This pricing model aligns with Ethereum’s long-term vision for modular scalability, economic sustainability, and equitable resource distribution. As rollups and blobspace continue to take centre stage in Ethereum’s execution landscape, fair aggregation pricing will be critical to ensuring healthy, sustainable network growth.

This is just the first iteration. As the ecosystem evolves and new dynamics emerge, we’ll revisit and refine the underlying game mechanics. Our goal is to stay ahead of the curve—continuously exploring how to make blob packaging on Ethereum as fair and efficient as possible.

Fair Fees for Shared Space: Pricing Blob Aggregation with Shapley Values