Gas, layer 2 and bridges

What a transaction costs, why layer 2 is cheaper — and which assumptions come with it.

This lesson has had no expert review. It was written for this platform and against the evidence it cites; nobody has gone through it independently.

Learning objectives

You can explain why transaction costs can consume a return.
You can name the additional risk a bridge brings into a position.

Check your prior knowledge

Answer these for yourself before reading on. Wherever you hesitate is where this lesson pays off.

Who receives the transaction fee?
Why do fees fluctuate?
What is a bridged token?

Core concept

Fact

Gas is a price for scarce block space

Every transaction consumes computation, and every block holds only a limited amount of it. The price comes from demand for that space, not from the transaction's value. A USD 200 reallocation costs the same as a USD 200,000 one at equal complexity.

Interpretation

Layer 2 moves execution, not trust

A layer 2 executes transactions off the main chain and anchors only the result there. That cuts cost substantially. It also adds an assumption: that the mechanism anchoring the result and resolving disputes works — and, depending on the design, that a withdrawal back to layer 1 observes a waiting period.

Risk

A bridged token is not the same token

Moving an asset to another chain generally creates a claim against the bridge there, not the original. It is worth what the backing on the origin side and the bridge contract's security make it worth. Two pools with apparently the same symbol on two chains can therefore carry different risks — and a portfolio holding both is less diversified than the line items suggest.

Definitions

Gas: The fee for a transaction's computation.
Layer 2: A network that executes transactions off the main chain and anchors results there.
Bridge: A mechanism that moves assets between chains, usually by locking and issuing a claim.

Model

The protocol's own risk
The risk of the chain it runs on
The layer 2 mechanism's risk, where one is involved
The bridge's risk, where the asset is bridged

What a position on another chain additionally carries — Each layer adds; none replaces another.

Formulas

A position's cost threshold

Minimum amount ≈ (gas costs for entry and exit) / expected net return

gas costs: sum of all transactions for entry, upkeep and exit
net return: expected return after protocol fees, as a decimal

Limit: The calculation assumes a known fee. Gas is itself volatile and typically rises exactly when many want to exit at once.

Worked example

Above what amount is the position worth it?

Gas for entry + exit: USD 60
Expected net return p.a.: 4 %
Intended holding period: 1 year

60 / 0.04 = 1,500

Below roughly USD 1,500 deployed, the fee consumes the entire annual return.

Reading: The quoted APY is before transaction costs. For small amounts and short holding periods the quoted figure is therefore systematically too high.

Interactive model

The worked example, with movable figures. Estimate first what happens — then check.

At what amount does the position pay off?

A fixed fee eats the whole return on small amounts — the threshold depends on yield and holding period.

Estimate first, then check

Estimate first: at what amount does a USD 60 fee eat exactly half of a 4 % annual return? And how does the threshold move if the holding period is only six months?

The starting values are the worked example's own figures — change one input at a time.

Amount

$0$7.5K

Planned holding period

Gas for entry and exit (USD)

Expected net yield (% p. a.)

What the model does not show: Gas is a fixed number here. In practice it varies with network load, and the return is an expectation, not a commitment. Both are assumptions and should be marked as such.

Retrieval

The transaction's value.The computation required and current demand for block space.The size of the expected return.

The position is diversified across two chains.The bridged side additionally carries the bridge's risk; diversification is smaller than it looks.Both sides are identical because the symbol is the same.

Exercise on real data

Find the same protocol on two chains. Note which of the four risk layers above differs between them — and which information you are missing to decide.

Compare chains in the Explorer →

Application

A product advertises 6 % APY on a layer 2. Which two figures do you need to estimate the return actually achievable?

Related case studies

CASE-04 — A dependency chain across four protocols

Institutional reading

Bank: How should a layer 2's withdrawal period appear in liquidity risk?
Asset management: Does the cost saving justify the added dependency on bridge and layer 2 mechanism?

Key takeaways

Gas is priced by computation and demand, not by a transaction's value.
Layer 2 lowers cost and adds assumptions.
A bridged asset is a claim against the bridge.