Fees explanation

Network gas for different kinds of swaps (for current Uniswap-like DEXes) takes around:

Token pair	Gas for SaucerSwap V1	Gas for Pangolin	Gas for HSuite
ERC20 -> ERC20 swap	910000 Gas	910000 Gas	N/A
HBAR -> ERC20 swap	260000 Gas	260000 Gas	N/A
ERC20 -> HBAR swap	16800000 Gas	1680000 Gas	N/A

The third option (ERC20 -> HBAR) consumes more gas than others, because of the high cost of the WHBAR burning operation (inside exchange). Additionally 1 and 3 operations require Approval transaction, which costs ~0.05 USD.

HSuite doesn't work at the smart-contract level; it utilizes Hedera Token Service (HTS) and doesn't need an approval transaction either.

Approx USD cost of swaps on the table below:

Token pair	Fee for SaucerSwap V1	Fee for Pangolin	Fee for HSuite
ERC20 -> ERC20 swap	~0.0746 USD	~0.0746 USD	~0.0016 USD
HBAR -> ERC20 swap	~0.0213 USD	~0.0213 USD	~0.0016 USD
ERC20 -> HBAR swap	~0.1378 USD	~0.1378 USD	~0.0016 USD

Amount of fee charged by EtaSwap can be different for each adapter, it’s possible to change/adjust the fee for a particular adapter. Current fees:

Exchange	Fee by EtaSwap
SaucerSwap	0.3%
Pangolin	0.3%
HSuite	0.3%

Network fee always charged in HBAR, so make sure you have enough HBAR coins to pay network fee before swap operation.

EtaSwap fee charged in source tokens (note: for HSuite, EtaSwap fee charged in HBAR).

Unused slippage always returns to user.

Example 1:

You have 100 tokenA and you want to exchange it by max possible amount of tokenB. For example lowest rate you found by EtaSwap - it's SaucerSwap with rate 3 (1 tokenA costs 3 tokensB). So you initiate swap with default slippage 2.5%.

1. You sign Approval transaction for 100 tokenA (spending 0.05 USD)

2. You sign swap transaction ERC20 -> ERC20 (spending 0.07 USD)

3. EtaSwap charges a fee for the SaucerSwap operation, 0.3% deducted from your 100 tokenA, so you proceed with the swap using 99.7 tokenA.

4. You expect to receive 99.7 * 3 = 299.1 tokenB. By slippage rate 2,5% expected minimum income will be 291.6225. If exchange can satisfy this amount - transaction is successful and you receive from 291.6225 up to 306.5775 tokenB.

In total your spendings: 0.12 USD + 100 tokenA, your income 291.6225 - 306.5775 tokenB.

Example 2:

You have some amount of HBAR and you want to buy exactly 200 tokenC. For example, the lowest rate you found on EtaSwap is Pangolin with rate 5 (1 HBAR costs 5 tokensC). So you initiate a swap with default slippage 2.5%.

1. You don't need to sign Approval transaction, since you are spending root token.

2. You sign swap transaction HBAR -> ERC20 (spending 0.02 USD). Amount of allowed to spend HBARs will be calculated like: reverse rate * amount to receive + slippage + EtaSwap fee. Reverse rate will be: 1 / 5 = 0.2. So amount, that smart contract allowed to spend: 0.2 * 200 + 0.2 * 200 * 0.025 + 0.2 * 200 * 0.003 = 41.12 HBAR.

3. If exchange can satisfy this amount - transaction is successful and you receive exactly 200 tokenC.

4. You receive change (unused HBAR tokens), calculated by: 41.12 HBAR (sent to smart-contract) - 39-41 HBAR (amount spent by exchange to get 200 tokenC) - 0.12 HBAR (EtaSwap fee) = 0 - 2 HBAR.

In total your spendings: 39.12 - 41.12 HBAR, your income 200 tokenC.

Note: the examples above are calculated with 0% price impact.