How much gas is needed for a transfer?
Moving funds from NEAR or Aurora back to Ethereum involves two transactions with the second one being an Ethereum transaction. We (Aurora) have no control over (1) the market price of ETH or (2) the congestion of Ethereum, and therefore we have zero control over how much that second transaction will cost you.
Typically, a transfer of ERC-20 to Aurora requires around 70k gas on Ethereum (Approve + Lock). To transfer it back would take around 330k gas to finalize, up to USD300 that is. So transfers back might be more expensive.